We are lucky to be among the generation of people who have ________ and experienced the great social changes in our country. width=”144″ style=”width:108.1pt;background:white;padding:0cm 5.4pt 0cm 5.4pt”

下列各句中，表达得体的一句是（  ）

He paid for a seat, when he _____ have entered free.[ ]

David often forgets _____ his English book.

______ you look at it, the fast, exciting pace of life in New York city is fascinating and will continue to fascinate more and more people.