The teacher told the pupils that the United States of America _____ 50 states.
| A．was made of | B．made up | C．makes up | D．is made up of |
However, in ______ recent years, Niagara Falls have come to be appreciated more for their natural beauty as ______ wonder of nature.
| A．不填; a | B．the; the | C．不填; the | D．the; a |
The argument remains extremely heated ______ it is worthwhile for China to open its door to foreign cars.
| A．that | B．which | C．if | D．whether |
It’s been over a year since I ______ back from the countryside.
| A．come | B．came | C．will come | D．had come |
--- I’ve passed the driving test!
--- ______
| A．Well done! | B．I am afraid not. |
| C．That will do! | D．I’m glad to. |
I ______ pay Tracy a visit, but I am not sure whether I will have time this Sunday.
| A．should | B．might | C．would | D．could |