Question

_______ made vast contributions in improving the relationship between the United States and Soviet Union.
Robert Kennedy
President Clinton
President Nixon
President Ford

Answer 1

Nixon. RFK had very little influence on Soviet-American relations, since he never held high office or served in the Department of State. Clinton was President at a time the Russians were deeply concerned with themselves, and about all he did was annoy them by bombing Serbia, an ally from way back. Ford wasn't President very long, and was chiefly engaged in damage control from Watergate and struggling with the issues of inflation and stagnation.

Nixon was the originator of the idea of "detente," along with all its cultural exchanges, cooperation in space, et cetera. He also initiated the Strategic Arms Limitation Talks (SALT) which lead to the first treaty to actually put limits on nuclear weapons (although these were so far above reality they had essentially zero actual effect). I think he negotiated and signed the ABM treaty, too.