Seeing their teacher _______ into the classroom, they stopped _______ at once.

The winter of last year was extremely cold_____, it was the coldestwinter on record.[]

If he had worked harder, he _________.

The similarities between social networks are striking.—That ________ come as no surprise，because they are all products of the Internet.

News reports say peace talks between the two countries have ______ with no agreement reached. [ ]