Saw this question in one of Kaplan's SC practice sets:

Daunted by the threat of costly lawsuits, it was
decided by most American pharmaceutical
companies to abandon doing research in new
forms of contraceptives.
Choices:

(A) Same as above
(B) the decision of most American
pharmaceutical companies was to
abandon doing research in new forms of
contraceptives
(C) most American pharmaceutical companies
have decided to abandon research in new
forms of contraceptives
(D) research in new forms of contraceptives
was abandoned by most American
pharmaceutical companies
(E) most American pharmaceutical companies
decided on abandoning research in new
forms of contraceptives

I think the real choices are only E and C.
My rationale: The present perfect in C changes the meaning (i.e., "have decided" implies - to this day, that is the decision ; "decided" implies they decided at some point, and we don't know what the current state is). I think the original sentence intended to say that this was their decision at some point.
I know the "decided on abandoning" in E sounds awkward, but between changing the meaning and being awkward, I chose the latter.