Although medical science ______ control over several dangerous diseases, what worries us is that some of them are returning.
A．a(chǎn)chievedB．has achievedC．will achieveD．had achieved
B
考查動詞時態(tài)。由are returning(將會返回)可知“現(xiàn)在已經(jīng)成功控制”了，要用現(xiàn)在完成時。
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