问题 选择题

一种微粒的质子数和电子数分别与另一种微粒的质子数和电子数相同,则下列说法中错误的是…(  )

A.可能是不同的分子

B.可能是不同的离子

C.可能是一种离子和一种分子

D.可能是同位素

答案

C

A的说法是正确的,比如CH4、NH3、H2O、HF等;

B说法亦对,如NH4+、H3O+等;

D说法如35Cl、37Cl,正确。

C说法可根据电荷守恒来确定其错误。

阅读理解

阅读理解。

     Talk about a real-life hero! Ten-year-old Larry Champagne from St. Louis,Missouri, hit the brake (刹车) on

a runaway school bus. He saved himself and 20 other kids on board from disaster. It all happened in one terrible accident. On the way to school, the bus driver, Ernestine Blackman, suddenly fell ill. Seeing the car was running away, the other kids started to scream, but Larry ran to the front and stopped the bus.

      "At first I thought, 'We're going to die,'" says Larry,"but after I pressed the brake, I felt safe."

     Larry's speedy reaction made news all over the country. He appeared on TV shows as a hero. The bus

company gave Larry a big gift. His school hung a medal of honor around his neck.

     "My grandmother always tells me to do what's right," says Larry. He thanked his brother, Jerrick, 9, who

"helped me get the bus driver up" during the emergency (紧急情况). How did he know how to stop the bus?

Larry is something of a mechanic (机械师). He helps his grandfather work on his old truck."He gets his hands

dirty," says his grandfather. One thing is for certain: Larry knows where to find the brakes.

1. What did Larry do to save the runaway bus?

A. He parked it for the sleeping bus driver.

B. He helped all the kids climb out through the windows.

C. He dialed 911.

D. he pressed the brake.

2. When did Larry finally feel safe?

A. When the kids finally stopped screaming.

B. When the police officers arrived.

C. Once he pressed the brake, and the bus stopped.

D. When the bus driver started driving again.

3. Larry got the following as praise for his hero action Except _____.

A. appearing on TV shows

B. a scholarship from his school

C. a big gift from the bus company

D. a medal of honor

4. Larry thanked his brother Jerrick for _____.

A. helping him get the bus driver up

B. helping him work on his old truck

C. teaching him how to find the brake

D. teaching him how to stop the bus

5. The underlined sentence "Larry is something of a mechanic" tells us that ____.

A. Larry's job is a mechanic

B. Larry knows something about machines

C. Larry is a robot

D. Larry knows nothing about machines

填空题