美国人每天要用4 500亿加仑的水。这些量的水可以让纽约城淹没在96英尺深的水中。我们应该记住，在地球上的水并不是取之不尽的。

Sentence No. 1 Sydney is an important commercial, industrial and tourist centre on the south-east coast of Australia. It is Australia’s largest city with a population of more than three million.

Sentence No. 5 Every day, Americans use 450 billion gallons of water. Such amount would cover New York City to a depth of 96 feet. We must remember that water is not inexhaustible on earth.