1.The students go nowhere ____school.

1.The students go nowhere ____school.
a.except
b.except for
c.except to
d.except that
这里我选except同类之前的除外,为什么不是正确答案?
2.We were watching TV at home ____we caught sight of a firend of ours in the news program
a.since
b.while
c.when
d.that
请教我如何辨析when和while 的用法.
都是错的！