阅读下列短文，从所给的四个选项中，选出最佳答案

　Two boys, both of the same weight, sit on each side of a see saw（跷跷板）．How far must they be from the centre in order to keep the see saw balanced?

　By moving to different positions, they will soon find out that they have to sit at equal distances from the centre．Now, if one of them is heavier, the heavier boy has to be nearer to the centre to make the see saw balanced．

　Things to do．

　Take a stone in each hand． Can you find out which stone is heavier? If the two stones are about the same size, you may not be able to tell which one is heavier．

　Place a pencil on two piles of books and balance a ruler and move them until the ruler is balanced．Find out how far each stone is from the pencil． The stone nearer to the pencil is the heavier one． Now you know how a simple weighing machine works．

1．The writer wants to tell us ______．

[　　]

A．what see saw is like

B．how to keep a see saw balanced

C．how a simple weighing machine works

D．what a simple weighing machine is like

2．If two boys sit at equal distances on each side of a see saw, the boy in the higher place shows ______．

[　　]

A．he is taller　　　 B．he is shorter

C．he is heavier　　　D．he is lighter

3．A see saw is used ______．　　　

[　　]

A．to weigh which boy is heavier of the two

B．to find out the weight of a boy

C．to make a simple experiment

D．for playing

4．In the last paragraph the writer tells us to ______.

[　　]

A．make an experiment

B．make full use of pencils, rulers and books

C．weigh something with stone

D．make a simple weighing machine

5．From the passage we can gain____　　 ．

[　　]

A．pleasure　　　 B．experience

C．knowledge　　　D．entertainment

In Europe people hold the fork in the left hand and the knife in the right throughout the meal, a system that is generally agreed to be more efficient than the American zigzag（曲折的）method. Americans hold both the fork and the knife in their right hands throughout the meal, so they continually change their forks to the left hand when they have to cut their meat. It seems to be funny for the Europeans to see Americans busy changing their dinner sets, making a lot of noises. A few explanations for this American style are as follows:?

(1)Americans are practical and efficient. Since most of us are right-handed, it is reasonable to keep our working tools at all times in the right hand that can use them most efficiently.?

(2)Americans, the master of the New World are rebels（叛逆者）.They use the zigzag method to break the rules in the Old World and in this way they are thumbing their nose at Mother England. Americans are a restless kind. They do not like to sit in one spot for very long when dining.

(3)Forced to do so, they respond by “playing” with the silver.?

Whatever the reason for the practice, it is now certainly as American as apple pie. Europeans recognize this and are quick to attack it as evidence of American innocence（无知）of form. Arguments against the zigzag method rest not only on grounds of efficiency but also on those of tradition. In Old World dining, the knife is held in the right hand continually because it can serve as an instant defense against the uninvited intruders（入侵者）.However, such alertness（警觉） is out of place in the New World, as every American believes that this is the home of the brave. Americans juggle their silverware, perhaps, to show that they are not afraid and that one of them holding a fork is worth any number of them holding blades（刀）.?

Americans use _______ to hold their fork to pick up the salad.?

A. the right hand    B. the left hand?

C. both hands  D. either of the two hands?

As the masters of the New World, Americans use a different cutting method from that in the Old World to _______.?

A. show their independence of Mother England?

B. show their disrespect to Mother England?

C. add a new tradition to those in Mother England?

D. show off their creativeness to Mother England?

In the sentence, the word “juggle” probably means _______.?

A. hold   B. play with　　　C. pick up      D. lay down?

Which of the following statements is NOT true??

A. European people hold the fork in the left hand and the knife in the right hand.

B. The zigzag eating method is related to American characteristics.?

C. The zigzag eating method has become an American feature.?

D. European people will use the American method because of its efficiency.

Multitasking

People who multitask all the time may be the worst at doing two things at once, a new research suggests. The findings, based on performances and self-evaluation by about 275 college students, indicate that many people multitask not out of a desire to increase productivity, but because they are easily distracted (分心) and can’t focus on one activity. And “those people turn out to be the worst at handling different things,” said David Sanbonmatsu, a psychologist at the University of Utah.

Sanbonmatsu and his colleagues gave the students a set of tests and asked them to report how often they multitasked, how good they thought they were at it, and how sensation-seeking (寻求刺激) or imperative (冲动) they were. They then evaluated the participants’ multitasking ability with a tricky mental task that required the students to do simple mathematical calculations while remembering a set of letters.

Not surprisingly, the scientists said, most people thought they were better than average at multitasking, and those who thought they were better at it were more likely to report using a cellphone while driving or viewing multiple kinds of media at once. But those who frequently deal with many things at the same time were found to perform the worst at the actual multitasking test. They also were more likely to admit to sensation-seeking and impulsive behavior, which connects with how easily people get bored and distracted.

“People multitask not because it’s going to lead to greater productivity, but because they’re distractible, and they get sucked into things that are not as important.” Sanbonmatsu said.

Adam Gazzaley, a researcher at the University of California, San Francisco, who was not a member of the research group, said one limitation of the study was that it couldn’t find out whether people who start out less focused  toward multitasking or whether people’s recognizing and understanding abilities change as a result of multitasking.

The findings do suggest, however, why the sensation-seeker who multitask the most may enjoy risky distracted driving. “People who are multitasking are generally less sensitive to risky situations.” said Paul Atchley, another researcher not in the group. “This may partly explain why people go in for these situations even though they’re dangerous.”

67. The research led by Sanbonmatsu indicates that people who multitask ______.

A. seek high productivity constantly

B. prefer handling different things when getting bored

C. are more focused when doing many things at a time

D. have the poorest results in doing various things at the same time

68. When Sanbonmatsu and his colleagues conducted their research, they ______.

A. assessed the multitasking ability of the students

B. evaluated the academic achievements of the students

C. analyzed the effects of the participants’ tricky mental tasks

D. measured the changes of the students’ understanding ability

69. According to Sanbonmatsu, people multitask because of their ______.

A. limited power in calculation

B. interests in doing things differently

C. inability to concentrate on one task

D. impulsive desire to try new things

70. From the last paragraph, we can learn that multitaskers usually ______.

A. drive very skillfully

B. go in for different tasks

C. fail to react quickly to potential dangers

D. refuse to explain the reasons for their behavior

Millions of people visit Yosemite National Park every year to see the tall waterfalls and mountains. The mountains are a splendid sight when viewed from the valley floor. Lots of stores, hotels, and restaurants are needed to handle the crowds. Also, water, roads, and other service systems are part of the infrastructure(基础设施)that must be maintained.

Unfortunately, these systems are starting to break down. It’s not just in Yosemite but in national parks around the nation.

Yosemite is thirty years old according to Dennis Galvin, a National Park Service worker. The park is not only old but worn out. Two or three times as many visitors come every year. That is too many visitors for the park to deal with.

Four years ago a storm washed out a water pipeline in the Grand Canyon. The National Park service had to send water trucks to provide water for the visitors. Last month pipes almost broke again and roads had to be closed for a while.

Why hasn’t the National Park Service kept up the park repairs? There is a lack of money. The United States has 378 monuments, parks, and wilderness areas. Between three and four billion dollars are needed for repairs.

Yosemite is one national park that does have money for repairs. It has two hundred million dollars but cannot spend it any way it chooses. When the park workers started widening the road, they were forced to stop by the Sierra Club. The club claimed that the road work was damaging the Merced River that runs through the park.

A Sierra Club lawyer, Julia Olson, feels that the infrastructure needs to be moved out of Yosemite. That way less pressure will be put on the already crowded park.

According to the text, the mountains in Yosemite look most splendid when they are appreciated from _______.

A. the bottom of the valleys         B. the top of the mountains

C. the side of the mountains         D. the edge of the valleys

National parks like Yosemite in the U.S. find it increasingly difficult to meet the need of visitors because ________.

A. the transport management needs improving 

B. they spend too much on their service systems

C. their service systems frequently go out of order

D. they need help from environmental organizations

The main problem of Yosemite National Park is its _______.

A. rundown water pipes   B. overcrowdedness   C. lack of money   D. narrow roads

According to the text, the Sierra Club is most likely to be ______.

A. an environmental group              B. an information center 

C. a travel service                     D. a law firm

Scientists are uncovering the secrets of two port cities lost under the waters of the Mediterranean Sea, a researcher said yesterday.

Herakleion and Menouthis were rich and proud cities until something reduced them to rubble (碎石) and buried them in the mud beneath 30 feet of sea water, French underwater explorer Franck Goddio said at the American Geophysical Union conference.

“This is a mystery that is ongoing,” said Goddio, a founder of the European Institute of Marine Archeology, a Paris-based underwater research organization backed by the wealthy Hilti Foundation of Liechtenstein(列支敦士登基金会).

The destruction of the twin port cities has haunted Goddio ever since he happened upon the site about 15 miles from Alexandria while exploring sunken ships from Napoleon’s fleet.

Goddio and his group of expert divers, marine archeologists(海洋考古学家) and others, are using high powered vacuums, satellite navigation systems and sophisticated sonar(声纳) to excavate(挖掘) the sunken cities from underneath a carpet of silt about one meter (three feet) high.

Walls of shops, remains of streets and gold artifacts have been found and recovered.

Some experts believe that the port cities were destroyed by a series of massive earthquakes, much like the quakes scientists believe felled Troy(特洛伊城), Jericho and other ancient cities. The uniform direction of the collapsed columns and walls suggest an earthquake, Goddio said, but no fault lines have been found nearby.

Other researchers believe a massive wave, caused by either an offshore earthquake or a distant underwater landslide, could explain the catastrophe. Still others think rising seas and a shift in the Nile River outlet doomed the cities.

“The argument, as you can see, continues,” Goddio said.

The reason why the two port cities disappeared under the waters of Mediterranean Sea is that ______.

A. the two port cities were destroyed by huge earthquakes

B. the disappearance of the two port cities was caused by underwater landslide

C. rising seas and a shift in the Nile River outlet doomed the cities

D. the story didn’t tell us at all

From the story we can draw a conclusion that _______.

A. the two port cities were famous for their wealth and the mystery

B. the two cities belonged to France

C. some mysterious creatures from other planets destroyed the two cities

D. the American Geophysical Union conference was once held in one of the two cities

This article is probably from _______.

A. a scientific magazine       B. a report to the government

C. a school text book         D. a scientific report in a newspaper