1.This________(理论) helps to explain how animals communicate with each other.
2.The final cost could be as much as two________(十亿) dollars.
3.The________(猛烈的) winds buried the village in sand.
4.Across the________(地球), sea level varies by hundreds of feet.
5.An________(原子) is so small that we can not see it.
6.Smoking is________(有害的) to health，but some people cannot get rid of it.
7.Can you tell me when it came into________(产生)?
8.The new owners have tried to give the restaurant a more familyfriendly________(气氛).
9.________(氧气) is a kind of gas which is necessary for most animals and plants to live.
10.I was surprised by the________(出席) of so many people at the meeting.
答案 1.theory 2.billion 3.violent 4.earth 5.atom 6.harmful 7.being 8.atmosphere 9.Oxygen 10.attendance
