问题 选择题

小明同学用同一台显微镜,通过调整目镜和物镜以及准焦螺旋,观察同一标本四次.请问,其中视野最暗的目镜和物镜的组合是(  )

A.5倍、10倍

B.5倍、40倍

C.10倍、10倍

D.10倍、40倍

答案

显微镜的放大倍数等于目镜与物镜放大倍数的乘积.所以,选项A、B、C、D所显示的放大倍数分别是50倍、200倍、100倍和400倍.显微镜的放大倍数与视野大小、亮度的关系见下表:

放大倍数视野内细胞数目视野亮度
 小
所以,选项D所显示的放大倍数最大,视野最暗.

故选:D.

阅读理解

阅读理解。

     This Thursday, across the US, kids are skipping school (缺课) and going to work with their parents.

They'll be making copies, sending faxes (传真) and sweeping floors. This is because April 28 is Take Our

Sons and Daughters to Work Day all over the US. This holiday shows kids what it means to be a grown-up

in the working world.

      I still remember when this day started, I was very happy. Not only did I have the chance to miss school,

but I also got to sit in my dad's taxi all day long and we would go to a restaurant for lunch.

     But after only 20 minutes of driving around the city. I was very bored. I couldn't read my book in the car

as I would get carsick(晕车)and my dad didn't like to turn on the radio. I got hot and uncomfortable. people

wouldn't get into his taxi because they thought he already had a passenger: me-so nothing happened. It seemed

years before we went out for lunch. I actually started to miss school.

     While the point of the day is to give kids a chance to experience real-life jobs and give them an idea of the

possibilities (可能性) for their futures, I got something completely different from the day. I learned to

appreciate (重视) school. Where else do you get to play with your friends, do science experiments, read great

books and write stories all in one day?

     Just as you'll have to learn to love your job later in life, learn to love school now. If you don't already, try

spending the day at work with your dad.

1. When is the "Take Our Sons and Daughters to Work Day" all over the US?

A. On February 28.

B. On March 28.

C. On April 28

D. On May 28.

2. That day the writer was happy at first for the following reasons except ________.

A. she didn't have to go to school

B. she would work as a grown-up

C. she could sit in her father's taxi all day

D. she would go our for lunch with her father

3. Why didn't people get into the writer's father's taxi?

A. Because her father didn't like to turn on the radio.

B. Because they thought the writer was a passenger.

C. Because her father's car was hot and uncomfortable.

D. Because her father didn't stop to take any passengers.

4. Which of the following is NOT the purpose of the "Take Our Sons and Daughters to Work Day"?

A. To teach kids to appreciate school.

B. To give kids a chance to experience real-life jobs.

C. To give kids an idea of the possibilities for their futures.

D. To show kids what it means to be adults in the working world.

5. What did the writer learn that day?

A. It's boring to drive a taxi.

B. Working with dad is fun.

C. It's hard to make money.

D. School life is much better.

单项选择题