Scientists say it may be five years ______ it is possible to test this medicine on human patients．
| A．since | B．until | C．before | D．when |
（2013·大纲卷）The watch was very good, and he 20 percent down for it.
| A．paid | B．cost | C．bought | D．spent |
（2013·大纲卷）Four and half hours of discussion took us up to midnight,and Break for cheese,chocolate and tea with sugar.
| A．a;a | B．the; the | C．不填；the | D．a;不填 |
People develop______ preference for a particular style of learning at______ early age and these preferences affect learning.
| A．a; an | B．a;不填 | C．不填;the | D．the ;an |
It may not be a great suggestion. But before _______ is put forward, we’ll make do with it.
| A．a good one | B．a better one | C．the best one | D．a best one |
（2013·新课标Ⅱ卷)Four and half hours of discussion took us up to midnight,and break for cheese,chocolate and tea with sugar.
| A．a;a | B．the; the | C．不填；the | D．a;不填 |