产品一旦进入衰退期就要立即退出市场。
参考答案：错
---_____does he play football after school? --- He always plays football after school.
A．How often
B．How long
C．How much
D．How well
酸雨的形成主要是大量燃烧化石燃料或生物物质，将酸性化合物排放至空气中。( )
