美国在70年代中期发生了经济危机，这场危机主要表现为(      )

①经济停滞     ②工人罢工     ③物价下跌     ④通货膨胀

阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填人一个适当的词或使用括号中词语的正确形式填空。

    Air is all around us. It is around us as we walk and play. From the time we were born air is around us on every side. When we sit down, it is around us. When we go to bed, air is also around us. We live in air. We can live ____ food or water for a few days, but we can't live for more than a few ____ (minute) without air. We take in air.

    When we are working ____ running, we need more air. When we are ____ (sleep), we need less air .We live in air, ____ we can't see it. We can only feel it when it ____ (move). Moving air is called ____ (windy). How can we make air move? Here ____ (be) one way. Hold ____ open book in front of your face, close it ____ (quick). What can you feel? What you feel is air.