题目内容：

短文填空

The world is filled of many interesting s 1. . Some are unpleasant to our ears w 2.    others are very pleasant to hear. In single day you probably hear hundreds of sounds. All sounds are d 3.. Some may be loud, some sounds are high, others are low, some sounds are useful.

W   4.   sound we can’t talk or listen to each other. The ringing of the alarm clock wakes people up. The hooting（鸣笛声）of a car warns people of d  5. .Some sounds are harmful. When planes fly low over the land, the very loud sounds can damage ( 毁坏 ) the house. Very l 6. sound can even make people deaf.

We know sound travels about one kilometer in three seconds. In a thunder storm you see the lighting f 7. and then hear the thunder. This is because light travels much f 8.  than sound. Next time you see lighting count the number of seconds before you h  9. the thunder. Divide this number by 3. This will tell you how m 10. kilometers away the thunder storm is.