Even if  you are a good high-jumper, you can jump only about seven feet off the ground. You cannot jump any higher because the earth pulls you hard. The pull of the earth is called gravity.

   You can easily find out the pull of the earth. If you weigh yourself, you will know how much gravity is pulling you. 来源：

   Since there is gravity, water runs down hill. When you throw a ball into the air, it falls back down. Because of gravity, you do not fall off the earth as it whirls (旋转) around. 来源：

   Then, can we get away from the earth and go far out into space? Now you can do it, because spaceships have been invented. Then spaceship will go so fast that it can escape (逃出) the earth’s gravity and carry you into space. 来源：

In this passage, the word “gravity” means_______.来源：

   A. the pull of everything.           B. the force of attraction(吸引) among objects.

   C. the force which attracts objects towards the centre of the earth来源：

   D. the force which attracts the earth towards the sun.

When you slip(滑) you always fall to the ground because________来源：

   A. the earth always turns round.                   B. the earth has gravity

   C. the earth’s gravity is greater than your weight.     D. you are careless. 来源：

Gravity is strong that_______

   A. it can throw a ball into the air.           B. it makes you jump only seven feet.

   C. it can let you fly away from the earth.     D. it can keep everything on earth.

Because of gravity,________

   A. water flows everything.            B. we can go everywhere by ship. 来源：

   C. water always flows downwards.     D. fish can live in water.

We can get away from the earth by spaceship because________

   A. the spaceship goes very fast.       B. the earth can’t pull the spaceship.

C. the spaceship has a strong force.    D. the spaceship can jump higher than others.

Even if you are naturally shy, these three tricks will help you to quickly build a new social circle in any new city．
1．Take pictures
One of the great things about taking pictures at an event or party is that it gives you an excuse to get in touch with a person．Everybody loves seeing pictures of themselves，and it’s very easy after taking a picture to say “If you’d like I can email it to you”．This can be the seed that leads to new connections．The next time you hear about a fun event email your new contacts to let them know about it．
2．Eat alone in public
You might feel self-conscious eating by yourself but it has an important benefit：you are much easier to approach when you are alone．People may be afraid of interrupting you or being rude if you are in a conversation with someone else．Bring a book or newspaper to read (this will make  you feel less self-conscious)．Plus，having an interesting book with you will give others an excuse to start a conversation if they’ve read it．
3．Join a class，sports team，or club
Yoga，salsa dancing，volleyball，Toastmasters (a public speaking club)，a class for work，etc. Take up a new hobby or continue an old one!
These are all great places to meet new people，primarily because you will be forced to see the same people over and over again in the class．You will automatically make friends with them if you have a common interest and are forced to see each other again．
Tips：
* In the beginning．never turn down an invitation from someone，even if it’s something you wouldn’t normally do．
* Email your new friends with fun things to do instead of always asking what their plans are, If they have a better plan you can drop (放弃) yours and join them．This will help establish（建立） you as someone who is contributing value instead of just taking it (people want this in a friend) ．
*Don’t let little things in life upset you or be a negative person．People don’t want to be around someone like that！
【小题1】     can give you an excuse to start new connections．

A．Taking pictures of others	B．Eating by yourself in public
C．Reading interesting books	D．Joining group activities

Even if you are an experienced backpacker or climber，you need to know what to do if something goes wrong．It is not that Alaska is that much more dangerous than other places．It is no more hazardous than elsewhere，as long as the proper precautions(预防措施)are taken．So, being prepared is crucial to ensure a safe trip．
First of all，make sure you pack everything you will need for your trip．Even if you are traveling by car，pack clothes and gear for backpacking．Because of the bad weather, cars break down frequently. Pack a survival(生存)kit full with：a down coat, boots ,mittens, a hat, snow-pants，sleeping bags，candles，a flashlight，and high-energy food. If you are traveling by car , also pack extra belts, a shovel, and a chain.
If you are camping or hiking，make sure you know how to avoid bears．If you are lost in the wilderness, there is no doubt you will encounter them.
However，there is no need to be nervous．Just take these precautions：make noise as you walk，bears will avoid you；cook your food away from where you sleep，and store your food away from where you sleep，so the bears are not attracted．Both of these should keep the bear away．However，if you do encounter a bear，there are two different schools of thought．One is to make noise and scare the bear away．The other is to stand still and speak softly to get the bear to leave．If you are dealing with a brown bear，you can climb a tree，since it cannot follow．But，black bears can climb．If for some reason the bear attacks，play dead．Try to protect your head and neck，and hopefully the bear will leave its“dead” prey.
【小题1】The underlined word “hazardous” in Paragraph l most probably means________．

D
As they migrate（迁移），butterflies and moths choose the winds they want to fly with，and they change their body positions if they start floating in the wrong direction．This new finding suggests that insects may employ some of the same methods that birds use for traveling long distances．Scientists have long thought that insects were simply at the mercy of the wind．
Fascinating as their skills of flight are，migrating behavior has been difficult to study in insects because many long distant trips happthousands of feet above ground．Only recently have scientists developed technologies that can detect such little creatures at such great heights．
To their surprise，though，the insects weren’t passive travelers on the winds．In autumn，for example，most light winds blew from the east，but the insects somehow sought out ones that carried them south and they positioned themselves to navigate directly to their wintering homes．
Even in the spring，when most winds flowed northward，the insects didn’t always go with the flow．If breezes weren’t blowing in the exact direction they wanted to go，the insects changed their body positions to compensate．Many migrating birds do the same thing．
The study also found，butterflies and moths actively flew within the air streams that pushed them along．By adding flight speeds to wind speeds，the scientists calculated that butterflies and moths can travel as fast as 100 kilometers an hour．The findings may have real-world applications．With climate warming，migrating insects are growing in number．Knowing how and when these pests move could help when farmers decide when to spray their crops．
71．What’s the main idea of the text?
A．Insects migrate with the seasons．     B．Wind helps insects greatly in migrating．
C．Windsurfing insects have real direction．D．Scientists have trouble in observing insects．
72．Scientists originally thought that____________．
A．insects always waited for their favourable winds
B．insects chose the winds they wanted to ride
C．insects were just blown about by the wind
D．insects positioned themselves in the winds
73．It is not easy to stuay the migrating behavior of the insects because____________
A．the little creatures can fly very fast     B．they have no regular migrating courses
C．the wind’s direction is hard to foresee    D．their flight is long and high above ground
74．We can learn from the text that______________.
A．insects fly in the way birds do
B．insects travel more easily in autumn
C．insects never position themselves when flying low
D．insects rest a lot when the wind pushes them along
75．According to the passage，the findings can              ．
A．increase insects in number         B．instruct farmers when to spray
C．prevent climate warming       D．help protect insects

As if there weren’t enough of them in the world already, scientists have succeeded in cloning flies. The alike fruit flies are the first insects ever cloned, says the Canadian team that created them. The question everyone asks is why anyone would want to clone flies in the first place. She hopes that the insects , which are very easy to experiment with , will help to adjust the cloning process in other animals and even in humans, where the technique is being researched to aid production of therapeutic (治疗的) stem cells.
In cloning, the DNA-containing nucleus of an adult cell is injected into an egg whose own nucleus(细胞核) has been removed. At the moment, the majority of cloned mice, sheep and other animals die before birth. It is thought this is because the adult DNA is not properly ‘reprogrammed’.
Using flies, researchers might discover genes that are important for this reprogramming, and that have matches in other animals. That is because it is relatively easy in flies to knock out the function of a single gene and then attempt cloning with these cells, which will test whether that gene is important. If such genes are confirmed, then in theory cloned mammalian embryos(晶胚) might be grown in selected solutions that change the activity of those genes to improve the technique’s success rate. Although some groups have attempted to clone insects before, Lloyd says this is the first time it has been successful. The team used a slight difference on the standard cloning process: they transferred nuclei taken from embryos rather than fully-grown adult cells. They sucked several nuclei (pl)out of developing fly embryos, and injected them into a fertilized(已受精的) fly egg. From over 800 early attempts, they cloned five adult insects, the group reports in the journal Genetics.
【小题1】The best title of this passage probably is _______.