用“what从句 + be + 被强调成分”或“被强调成分 + be + what从句”表示强调。
John wants a good rest. 约翰想要好好休息一下。
--What John wants is a good rest. 约翰想要的是好好休息一下。
或： A good rest is what John wants. 好好休息一下正是约翰想要的事。（比较少见）
I'd like you to work on Exercise Two on Page 38. 我要你们做38页上的练习二。
-- What I'd like you to work on is Exercise Two on Page 38. 我要你们做的作业是38页上的练习二。
I need two books. 我要两本书。
-- What I need are two books. 我要的是两本书。（注意谓语动词的数）
注意：
避免说：Where you should play football is the play ground, not the classroom.
最好说：The place where you should play football is the playground, not the classroom. 你们踢足球的地方是操场，而不是教室。
避免说：When I read English aloud is early morning.
最好说：The time I read English aloud is early morning. 我是在清晨朗读英语。
避免说：Why she was absent from class was that she was feeling unwell.
