---Why does the Lake smell terrible?
---Because large quantities of water .
| A．have polluted | B．is being polluted |
| C．has been polluted | D．have been polluted |
Lucy knew nothing about it ________ her sister told her.
| A．because | B．until | C．if | D．since |
He walked ________ fast for us ________catch up with.
| A．so, that | B．such, that | C．enough, to | D．too, to |
_______ my mother ________ my sister watches TV plays these days.
| A．Either, nor | B．Both, and | C．Neither, or | D．Neither, nor |
The nurse doesn't feel well today, _________ she still works very hard.
| A．but | B．and | C．or | D．when |
Tom has been in the factory _________he left school.
| A．when | B．since | C．as soon as | D．whether |