Brinksmanship is a strategy in which you force compliance by threatening an overwhelming, disproportionate response. It is very high-risk, but it can also be effective.
Eisenhower's brinkmanship policy in the Cold War was to threaten immediate retaliation with nuclear weapons if the Soviet Union attempted to invade any US allies. On the one hand, this made the Soviet Union wary about invading any US allies, which is a good thing; on the other hand, if they ever tried to call our bluff, we would either have to back down and lose credibility or launch a nuclear war.
Let's go through the options to see which has the least to do with that policy.
A strong Air Force isn't necessarily a brinksmanship policy, but in Eisenhower's case it was, as it was during this period that B-52s and ICBMs were developed in order to maximize the ability to deploy nuclear weapons. So that has at least a little bit to do with Eisenhower's brinkmanship policy.
Massive retaliation is the essence of brinksmanship policy; the whole point is that in response to any violation you retaliate with overwhelming force. Far from being unrelated, it's basically the exact same thing.
But "flexible response", that's quite different. In fact the term "flexible response" was first used by Kennedy---after Eisenhower left office---to describe a policy where we would maintain nuclear weapons as an option, but also build a large conventional army capable of responding to smaller threats in a more proportionate way. The idea was to prevent the Soviet Union specifically from using nuclear weapons---if they used nukes, so would we; but as long as they limited themselves to conventional arms we would as well. (Actually there was one exception; the flexible response doctrine allowed that if a US ally were about to be overwhelmed, even by conventional forces, they could deploy small-scale "tactical" nuclear weapons.) Kennedy was trying to de-escalate the Cold War away from nuclear annihilation. He succeeded, insofar as we are still alive; but there were definitely a number of close calls (such as the Cuban Missile Crisis).
The best answer is therefore (c), since that refers to a policy implemented by Kennedy, not Eisenhower, and furthermore a policy that was intended to reduce brinksmanship.