—Why does the lake smell terrible?
—Because large quantities of water_____.
| A．have polluted | B．is being polluted |
| C．have been polluted | D．has been polluted |
It is these poisonous products _______can cause the symptoms of the flu, such as headache and aching muscles.
| A．who | B．that | C．how | D．what |
It was ____ I met Mr Green in Shanghai.
| A．many years that | B．many years before |
| C．many years ago that | D．many years when |
Was it because he was ill ____ he asked for leave?
| A．and | B．that | C．that’s | D．so |
It was on October 1st ____ new China was founded.
| A．which | B．when | C．as | D．that |
It was in the rice fields ____ we had our league meeting.
| A．where | B．that | C．in which | D．on which |