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：考查时态：句意：虽然医学科学已经控制了几个危险的疾病，让我们担心的是一些又回来了。从第二句话用的进行时，可知前面是已经控制了，用现在完成时。选B。