He is really nervous. He ______back and forth all the night waiting for the results.
The teacher suggested we ________ as many books as we can.
—It’s a long time ________ I saw you last.—Yes,and what a pity it is now that it will be a long time ________ we see each other again.
The ________ look on her face suggested that she ________ it before.
—What time would you like me to ________ this evening for the concert?—I think 6∶30 will be OK.
—Does he know how to work out the problem?—Yes,he has ________ a good idea to solve it.