问题
选择题
Although medical science __________ control over several diseases,what worries us is that some of them are returning.
A．achieved
B．has achieved
C．will achieve
D．had achieved
答案
答案：B
题目分析：句意：虽然医疗科学已经控制了几种疾病，我们担心的是有些还会回来。从what worries us is that some of them are returning.可知现在强调的是现在的结果，所以用现在完成时，选B.