John Snow found that the polluted water was _________for the outbreak of cholera.

Confronted with the complex international situation,we need a foreign policy that is more ____.

I have warned you not to do that but you turned a deaf ear to me.[ ]

Alice, why didn’t you come yesterday? –I _________, but I had an unexpected visitor.

Professor Wang, together with hiscolleagues, _______ working on the project day and nightto _______ thedeadline.