Eg. I Do give you the book.
what分句＋be + 动词的不定式eg. He gave her a book.------What he did was (to) give her a book.
what分句＋be + 动词的分词He will be taking a plane to Beijing---What he will be doing is taking a plane to Beijing
He has finished his homework.----What he has done is finished(finish/to finish) his homework.
Pesudo - cleft
I gave him a letter.
What I did is give him a letter
what 分句＋be + 名词词组
Eg. He gave her a book.
What he gave her was a book.
A book was what he gave her.