阅读理解。
Many earthquakes (地震) happen without warning, so it is important to know what to do wherever you
are during an earthquake. Here are some top tips on how to stay safe in an earthquake.
◆ Keep a cool head. Worry may make bad decisions. Think about what you should do. The first several
seconds are important.
◆ If you are indoors during an earthquake, hide under a heavy desk and protect your head. Stay away from
windows and anything that could fall on you.
◆ If you are in a crowded hall away from the door, don't rush to the exit. You will find too many people
trying to get out at the same time. Instead, hide under a desk or a table. Do not get into a lift during an
earthquake!
◆Stay in a safe area until you are sure it's OK to leave. Some aftershocks (余震) may follow an earthquake.
These are as dangerous as the earthquake.
◆If you are at home and you smell gas, open a window and leave the building quickly.
◆ If you are outdoors, find a clear place away from buildings, trees, street lights and power lines.
◆If you are buried in debris (埋在废墟), you may make noises by knocking at the rocks. Shouting will use
up your energy. You could be without help for up to 72 hours. Try to find some water and food. These are
important for you.
1. The underlined words "top tips" mean _________.
A. useful advice
B. boring news
C. interesting stories
2. If you are in a crowded hall away from the door when an earthquake happens,
you mustn't try to get out because _________.
A. it's more dangerous outside
B. you may lose the way
C. people may hurt each other when rushing out at the same time
3. Which one is right during an earthquake?
A. If you smell gas, stay at home and wait for help.
B. Hiding under a heavy desk if you are indoors.
C. Using the lift to go downstairs.
4. You should _________ if yo u are buried in debris.
A. find a clear place
B. keep shouting for help
C. catch people's attention by knocking at the rocks
5. From the passage we know that _________.
A. keeping a cool head is very important during an earthquake
B. we can hide under the tree during an earthquake
C. we needn't care about aftershocks
得
，则
，即B再次回到距离地面高度为
时速度的大小也为
。此后B做竖直上抛运动，落回距离地面高度为
时速度的大小还是
。
次离开地面时速度的大小
次离开地面上升的最大高度为
