If there is a lot of work ________， I'm happy to just keep on until it is finished.
| A．to do | B．to be doing |
| C．done | D．doing |
We are really disappointed to see millions on earth who have nothing but hunger and cold __________ no chance to improve their life .
| A．to have | B．having |
| C．having had | D．have |
We are roommates for 3 years and never once __________ .
| A．we have quarreled | B．have we quarreled |
| C．do we quarrel | D．did we quarrel |
I will never forget the park __________ I spent so many happy hours there with my parents last summer .
| A．where | B．because |
| C．which | D．so |
In fact , the hazy weather problem is so severe now that it has aroused __________ nationwide concern about __________ environmental pollution .
| A．/ ; / | B．/ ; the |
| C．a ; / | D．a ; the |
– I spent three hours buying a train ticket at the railway station the other day .
-- Why ? You __________ one on the Internet or by phone .
| A．could have bought | B．must have bought |
| C．would buy | D．should buy |