He made another wonderful discovery, ______ of great importance to science.
| A．which I think is | B．which I think it is |
| C．which I think | D．I think which is |
Professor White has written some short stories, but he is＿＿＿known for his plays．
| A．the best | B．more | C．better | D．the most |
—— Have you seen＿＿＿pen? I left it here this morning．
—— Is it＿＿＿black one? I think I saw it somewhere．
| A．a； the | B．the； the | C．the； a | D．a； a |
Many people agree that＿＿＿knowledge of English is a must in＿＿＿international trade today．
| A．a；／ | B．the； an | C．the； the | D．／； the |
How beautifully she sings! I have never heard＿＿＿＿．
| A．the better voice | B．a good voice | C．the best voice | D．a better voice |
If there were no examinations, we should have＿＿＿＿＿at school．
| A．the happiest time | B．a more happier time | C．much happiest time | D．a much happier time |