问题补充:
is known to everybody that the moon travels round the earth.
A. It
B. As
C. When
D. Where
答案:
(答案→)A. It
B. As
C. When
D. Where
解析:考察it作为形式主语。本句中的It是形式主语,真正的主语是后面的that the moon travels round the earth。这里的that只是一个引导词而已,不在句中充当任何成分。句意:众所周知的事情是月球绕着地球转。故A正确。