阅读理解。

    The air around us is important to everyone. Without air, we couldn't live. Everyone

understands that. But air is important in many other ways-ways that are not always widely

known. For example, if we didn't have air, there would be no sound. Sound travels through

air. Without air, there would be no fire.

    There would be no cars, cars need air to start. Without air, there would be no wind or

clouds. There would be no weather, as we know it. the night time would be very cold and

the days very hot. We would have to look for shelter (遮蔽) from the sun, as there would

be no atmosphere (大气)to protect (保护) us from the sun's deadly rays (光线).

1. _____ understands we couldn't live without air. [ ]

A. No one

B. Someone

C. Everyone

D. All of us

2. If we didn't have air, the night time would be very _____. [ ]

A. hot

B. short

C. cold

D. long

3. Without _____, cars can't start. [ ]

A. air

B. sound

C. wind

D. clouds

4. _____ protects us from the sun's deadly rays. [ ]

A. The surface (表面) of the earth

B. The cold wind 　

C. The atmosphere

D. The weather