During the 1980s it became clear that soliciting private funds was far more efficient for environmentalists who sought financial aid than to go to state or federal agencies.
Answer
(B) That for environmentalists who sought financial aid, it was far more efficient to solicit private funds.
During the 1980s it became clear {that for environmentalists who sought financial aid, it was far more efficient [to solicit private funds] than (to go to state or federal agencies).}