He was interested in a________ and always stayed up at night to watch the stars.
Not long ago a v________ earthquake occurred off the coast of Indonesia.
Computer hackers have broken down security s________, raising questions about the safety of information.
Too much sugar can be h________ to children’s teeth.
The three-star hotel offers a friendly a_______ and personal service.
China has sent up another ________(人造卫星) into space.
There is a lot of rubbish ________(漂浮)on the surface of the river.
________(理论)is based on practice.
The ________(气候)is different from palce to place.
6 ________(乘)by 5 is 30.