Liu Xiang has announced the end of his sporting career.— . But I think he is still one of the greatest athletes in China.

We have done things we ought not to have done and ______ undone things we ought to have done

Jenny, _________ do you visit your grandparents— Twice a month.

ack, I just can’t get my car started. I think there’s something wrong with the engine.—Oh, let me see. Ah, that is not _______ it is. Actually, your car has used up all the petrol.

If only we ____ then the disease was curable.[ ]