题目

When the weather is hot, you go to a lake or an ocean. When you are nears lake or an ocean, you feel cool. Why? The sun makes the ear& hot, but it cannot make the water very hot. Although the air over the earth becomes hot, the air over the water keeps cool. The hot air over the earth goes up. Then the cool air over the water moves in and takes the place of the hot air. When you are near a lake or an ocean, you feel the cool air. When it moves in, you feel the wind. And the wind makes you cool. Of course, scientists cannot answer all of our questions, ff you ask, Why is the ocean full of s生物防治是现在及今后农、林、牧业防治害虫的主要方法,现在主要有:以虫治虫、以鸟治虫及以菌治虫等措施,除下列哪一项外都是其优点  (      ) A.可以少用或不用农药,减少农药对环境的污染 B.自然界中所有的农作物害虫都能用生物防治来消灭 C.可以节省防害的成本,提高农业生产的经济效益 D.减少生产环节,降低开发成本且治虫的效果可持续
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