问题描述：
1、I don't know _______ to do.
A、what B、how C、where D、when
2、She spent much time in _______ for the test.（prepare）
3、What _______ when we boil water?（happen）
4、A：Where is Bob?
B：Everybody knows that water _______ at 0℃.（freeze）
A、what B、how C、where D、when
2、She spent much time in _______ for the test.（prepare）
3、What _______ when we boil water?（happen）
4、A：Where is Bob?
B：Everybody knows that water _______ at 0℃.（freeze）
问题解答：
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