--When _______ you _______ to learn to skate?--Five years ago.
| A．do , begin | B．will , begin | C．have , begun | D．did , begin |
The first thing _____ I should do is to work out a study plan for the next term.
| A．which | B．that | C．what | D．if |
_____ of the water _____ polluted. We must try to protect our environment.
| A．Two third; are | B．Two third; is | C．Two thirds; are | D．Two thirds; is |
He is so poor that he has no house _____.
| A．to live | B．living | C．living in | D．to live in |
The stones are so heavy. How _____ they _____ to the top of the building without modern machines?
| A．do; lift | B．did; lift | C．were; lifted | D．were; lift |
No free plastic bag in the supermarket helps to _____ white pollution.
| A．reduce | B．recycle | C．provide | D．produce |