The rivers will become dirtier and dirtier ______ we take action to protect them.
A. since B. if
C. until D. unless
He often takes time______summer holiday with his grandparents.
A. to spend B. spend C. spent D. spending
Nobody can predict what in the future．So enjoy your life．
A. will happen B. Happen C. have happen D. happen
—With the help of your friends，you’ll deal with the problem better，John．
— Why didn’t I mink of such a good idea?
A. Why not? B. You have a point． C. Well done． D. That’s all right．
The students ________ don’t study hard will not pass the exam.
A. which B. who C. whom D. whose
一Why were you late for schoo1 this morning?
—Because my alarm clock didn’t go off and I ．
A. changed B. completed C. overslept D. missed
