Measures must be taken before there is another collapse of the coal mine, ______?
| A．must they | B．mustn’t they | C．is there | D．isn’t there |
Have you ever seen any trees ________ leaves were black because of the polluted air?
| A．whose | B．that |
| C．which | D．who |
The scientist won the Nobel Prize in Chemistry, ________ made him famous all over the world.
| A．this | B．that |
| C．what | D．which |
The result was not the same ________ the professor had expected, ________ was rather disappointing.
| A．as; which | B．which; as |
| C．as; that | D．that; which |
Was it through Mary, ________ was working at a high school, ________ you got to know Tom?
| A．who; who | B．that; which |
| C．who; that | D．who; which |
Nowadays people are more concerned about the environment ________ they live.
| A．what | B．which |
| C．when | D．where |