Although medical science control over several dangerous diseases, what worries us is that some of them are returning.
A. achieved
B. has achieved
C. will achieve
D. had achieved
网友回答
A. achieved
(答案→)B. has achieved
C. will achieve
D. had achieved
解析：考查动词时态。由are returning(将会返回)可知“现在已经成功控制”了，要用现在完成时。