We’re so busy that no one in the office can _____ for any other work.
--- Are you satisfied with what he has done? --- Not at all. It can’t be ________.
Last week the students did the experiment in order to_______ if iron rusts in dry air.
--- Did you enjoy the party last weekend at Peter’s home? --- Oh, sure. It has been years _______ I last enjoyed myself like that.
Mike failed to finish his homework on time, so he tried to avoid _______ his teacher.
--- How do you find Mr Li’s lecture? --- Good indeed. It_______ many problems we have come across in our study.