The scientist __________ the experiment for half a year, but he _______ yet.
A．made; didn’t succeedB．made; hasn’t succeeded
C．was making; didn’t succeedD．has been making; hasn’t succeeded
D
考查時態(tài)。根據(jù)for half a year可知應該使用完成時，再根據(jù)句意可知完成進行時符合句子的意思。Yet也和完成時連用。結合句意可知D正確。句意：半年來那位科學家一直在做那個實驗，但他還沒有成功。
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