问题 选择题

如图所示a、b两颗绕地球运行的卫星,b是地球同步卫星,以下说法正确的是

A.卫星a运行周期大于24h

B.卫星a运行周期小于24h

C.在地面附近发射卫星b的速度为11.2km/s

D.卫星a的运行速度可能为7.9km/s

答案

答案:B

题目分析:b是地球同步卫星,则,由牛顿第二定律知,而。故,选项A错误、选项B正确;要使卫星成为地球的卫星需要的发射速度是,选项C错误;若卫星为近地卫星,,其线速度,选项D错误;故选B.

多项选择题
阅读理解

阅读理解。

     An ichthyologist is a scientist who studies fish. Most people who do this job say they love their work

because it is very rewarding and varied. They work not only inside a laboratory, but also out in the field.

Fieldwork includes traveling to river? oceans and lakes in order to collect information and specimens (~2~),

reading, writing and speaking me also very important to the job, fish scientists need to read the research of

other scientists. They must he able to write up their own research clearly so that others can follow it. They

also need to be able to give lectures about their findings, so that they can spread knowledge.

      Ichthyologists who wish to specialize can choose any one of three areas of study. The first area is

aquaculture (水产养殖). This involves the study and practice of fish farming and management. Because it is

a rather new study, there are very few job opportunities available. However, as there is so much to discover,

many see it as an exciting area for a new ichthyologist to enter. The second area is fisheries science, which

means working with a team of scientists to find out more about different fish species. The third area is about

the protection of natural fish populations. This is very important today, given that many fish species are in

danger of dying out because of the actions of humans.

     To become a successful fish scientist, you need to have a curious mind and be able to work on your own.

You also need to be able to handle equipment and perform experiments; but most importantly, you must love

fish. To become an ichthyologist, you will need to train at a university to pass a Bachelor of Science degree.

For this, you will need to be good at mathematics, physical science and biology. Then, you will need to study

for another year to complete an honours degree in ichthyology. This honours degree contains coursework

about all aspects of fish. You also need to complete a research paper.

1. What makes the jobs of ichthyologists so varied?

A. They study fish habits and collect information.

B. They have to study science and mathematics.

C. They work in fields as well as in laboratories.

D. They read research papers written by others.

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

A. An ichthyologist has an interesting and varied profession.

B. Aquaculture is the study of fish protection.

C. The life of an ichthyologist can involve lots of travel.

D. A fish scientist needs to be independent and curious about things.

3. Who is most likely to become an ichthyologist?

A. Tom, because he likes fishing and outdoor sports.

B. Jack, because he likes to travel and read adventure books.

C. Jenny, because she likes science, mathematics and reading about dinosaurs.

D. Jane, because she likes mathematics, science, biology and searching rock-pools.

4. The passage is probably written for _____.

A. university students

B. science researchers

C. fisheries experts

D. fish farmers