The river will be dirtier and dirtier________we do nothing to protect them．
| A．since |
| B．if |
| C．unless |
| D．until |
Mary sings English songs well and ______.
| A．Jane does too | B．either does Joes | C．so Janes does | D．so does Jane |
I mean ______ class meeting on Monday afternoon.
| A．have | B．to have | C．having | D．to having |
Beijing is one of the ______ in the world today.
| A．busiest city | B．busiest cities | C．busy city | D．busy cities |
No matter what you do, you can’t change the situation.
| A．whoever | B．wherever | C．whatever | D．what ever |
The story reminded me ______ an experience I once had.
| A．of | B．to | C．at | D．On |