主语从句和同位语从句

1.Itisobvioustothestudents_______theyshouldgetwellpreparedfortheirfuture.

A.which?????????????B.that?????????????C.whether?????????????D.as

【答案解析】B

【详解】考察主语从句。句意：学生们明显应当为他们的将来做好充分的预备。此句用it做形式主语指代主语从句“___theyshouldgetwellpreparedfortheirfuture”，引导词在主语从句中不做任何成