The committee urged that actions ________ to control pollution.
| A．must be taken | B．could be taken |
| C．might be taken | D．should be taken |
Nowadays people are more concerned about the environment _______ they live.
| A．what | B．which | C．when | D．where |
There is no simple answer, _____ is often the case in science.
| A．as | B．that | C．when | D．where |
Finally he reached a lonely island _________ was completely cut off from the outside world.
| A．when | B．where | C．which | D．whom |
He wrote a letter ______ he explains what had happened in the accident.
| A．what | B．which | C．where | D．how |
The president of the World Bank says he has a passion for China, ______ he remembers starting as early as his childhood.
| A．where | B．which | C．what | D．when |