I can’t carry the big box. Can you help _____?

What do you think of Ann?—Ann is so careful that she always goes over her exercises to ______ there are no mistakes.

When has the country been open to internationaltrade?—_____1978 , Isuppose

Only then ________ that he had lost a good chance of achieving his dream.

_____ hat is Mrs Li’s. It’s _____ old one.