单选题：He commanded the students ______ the classroom before he ret..

If I ________ your advice then, I think that the crops could be growing better.A．tookB．would have takenC．had takenD．have taken

I insisted that a doctor ________ immediately.A．has been sent forB．sends forC．be sent forD．will be sent for

I’ve ordered some pizza, so we _______ worry about cooking when we get home tired.A．can’tB．dare notC．needn’tD．may not

It’s required that the students______ mobile phones in their school, so seldom ______ them using one. A．not use; will you seeB．should not use; you will see C．don’t use; will you seeD．would not use; you will see

—Jack fell off the ladder yesterday，but he is all right now.—What a lucky dog! He________ himself badly.A．should injureB．might injureC．should have injuredD．could have injured