Some unfortunate people are rather attractive to mosquitoes, while the smell of some lucky people drives the blood-suckers away. Now the smelly chemicals from the sweat of these lucky people have been 题目和参考答案——青夏教育精英家教网—

题目内容

Some unfortunate people are rather attractive to mosquitoes, while the smell of some lucky people drives the blood-suckers away. Now the smelly chemicals from the sweat of these lucky people have been identified by researchers, who are testing its effectiveness as a natural mosquito repellent (驱蚊剂).

Everybody produces a mixture of chemicals with smells in their sweat, some of which attract biting insects. But people who do not get bitten also produce smelly chemicals that appear to mask the smells of the attractive chemicals.

This masking is very effective in avoiding a mosquito’s bite, explains James Logan, a scientist who carried out the research with his colleagues.

These helpful chemicals probably occur naturally in everybody’s sweat but some people have a much higher ratio (比例) than others.

“It’s very exciting,” Logan says, “because these are totally natural chemicals with an effectiveness that compares favorably to other chemicals such as DEET, which is the best repellent available but has unwanted side effects.”

A key chemical identified by Logan as a repellent is also “a natural food additive which has been proven safe”. He says, “And because it can be made by plants, it may one day be possible to mass-produce it cheaply.”

The repellent is currently being tested by 16 volunteers in Africa. Meanwhile, the researchers are testing the repellent against other biting insects.

49．Which can be concluded from this passage?

A．Mosquitoes like to suck attractive people.

B．Only some people produce a smelly substance in their sweat

C．The cost of plant-related products can be low.

D．Some chemicals contained in people’s sweat can be eaten as food.

50．What is the main idea of this passage?

A．Some people are luckier than other people

B．Scientists help us to avoid the inconvenience of the biting insects

C．Scientists have found a natural anti-biting substance in people’s bodies.

D．The natural mosquito repellent is good for people.

51．Why are some people less attractive to mosquitoes?

A．Because they have less sweat

B．Because their sweat contains a particular chemical.

C．Because the ratio of their natural mosquito repellent is much higher

D．Because they are less attractive

52．Which of the following statements is NOT true according to this passage?

A．Scientists are doing experiments with volunteers in Africa.

B．The natural mosquito repellent is only used to deal with mosquitoes

C．DEET is the best repellent available now

D．All people might produce chemicals that can mask the mosquito-attracting substance.

CCCB

练习册系列答案

68所名校图书小升初高分夺冠真卷系列答案

伴你成长周周练月月测系列答案

小升初金卷导练系列答案

萌齐小升初强化模拟训练系列答案

相关题目

Dear editor,
My name is called Zhang Hong. I am a middle school	76．
student. When I go to the school every day, I can see a lot of	77．
sellers outside around our school walls, sell vegetables, fruits,	78．
fish, meat and so on. Some even make dishes in the opening air.	79．
They often shout at the top of their voices in order draw the	80．
passers-by’s attention. We could hear the noises in the classroom	81．
and cannot concentrate on our lessons. Beside, they also make	82．
the streets dirt, smelly and crowded. What a shame!	83．
How we want to get the situation improved and have our	84．
lessons in a quiet place! That’s how I write to you for help!	85．

As some famous singers will appear at the pop concert ,___ likely to be a large audience.

A. it’s B. here’s C. there’s D. that’s

We can see clearly from the top of the building_____________ that the police are talking to．

A．what is it B．who it is

C．how is it D．where it is

Ads are usually broadcast on TV and over radio, posted on Internet and printed in newspapers and on

posters in our cities.

A．the; X; a; the; the B．X; X; the; X; X

C．the; a; the; X; the D．X; the; the; X; X

She stood there in the rain, for the bus .

A．waiting; to arrive B．waited; to arrive

C．waiting; arriving D．waited; arriving

Some equipment as well as a number of maps and books ______ to the area since the earthquake occurred.

A. has been offered B. have been offered

C. is being offered D. are offered

_____, we have the correct leadership of the Party.

A. To start with B. To begin C. To start D. At begin

Seen from the moon, our earth, with water ____ 70% of its surface, appears as a “blue ball”.

A. covers B. covered C. to cover D. covering

试题分类