which policy was central to the foreign policy of every president from truman through johnson? a) detente b)containment c)massive retaliation d)democratic enlargement

I'd go with (B) containment. They wanted to contain communism by building up an alliance of friends around the world to "box in" communist influence or countries that fell under their control. The other answers don't make much sense - at least not yet. Detente happened much later under Nixon and Ford, a kind of thawing period between the US and the Soviets. Massive retaliation was the military policy at the time, not their foreign policy, and democratic enlargement is something associated with President Clinton.