It may take _________ years to make such robots .

What’s the noise ? It sounds as if it comes from upstairs. –______. It must be the window-cleaner working , next door.

What should we say when we meet Americans __________ the tirst time.[ ]

_________ are all the gifts?[ ]

He did not write _________,though(尽管)he had______ ­­­­­­­­­­­。