Although medical science ________ control over several dangerous diseases, what worries us is that some of them are returning．

1. A.
   achieved
2. B.
   has achieved
3. C.
   will achieve
4. D.
   had achieved

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

Although medical science________ control over several dangerous diseases, what worries us is that some of them are returning.?

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