---- Why does the river smell terrible?
---- Because large quantities of water______．
| A．have been polluted | B．has polluted | C．has been polluted | D．have polluted |
When you learn a foreign language, ________you must forget your own one.
| A．above all | B．after all | C．in all | D．at all |
Mark ______ a basketball game in the stadium that _______ 5000 people.
| A．holds; is holding | B．is holding; holds |
| C．holds; holds | D．is holding; is holding |
The conference has been held to discuss the effects of tourism ______ the wildlife in 
the area.
| A．in | B．on | C．at | D．with |
Our son doesn’t know what to _____ at the university; he can’t make up his mind about his future.
| A．take in | B．take up | C．take over | D．take after |
We won’t give up _____ we should fail ten times.
| A．even if | B．since | C．whet her |
D．until |