Since nobody gave him any help，he ________ have done the research on his own.

The new supermarket announced that the first to purchase goods on the opening day_______ get a big prize.

It has been announced that students _______ remain in their seats until all the papers have been collected.

 — Are you going to Beijing by air?— It’s fast, but expensive. So I’m not sure. I _____ take a train. 

Every time they met, they ____ talk about former classmates they remembered.