Concept : Assumption is not stated in the argument directly and its a link between the premise and the conclusion.
Conclusion: Thus, no one—including those making marital vows—should take “love” in this context to be referring to feelings.
(A) None of our feelings are within our control.
This is directly given in the argument. Eliminate. Reference : "for feelings are not within one’s control"
(B) People should not make promises to do something that is not within their control.
This has got nothing to do with our conclusion and is not an underlying assumption. Out of scope
(C) “Love” can legitimately be taken to refer to something other than feelings.
This isn't an underlying assumption and has got nothing to do with the argument in hand. Out of scope.
(D) Promises should not be interpreted in such a way that they make no sense.
Voila. The right answer.
As per argument, If “love” here refers to a feeling, then this promise makes no sense.
Now option D says Promises should not be interpreted in such a way that they make no sense. Lets negate this, Promises
should be interpreted in such a way that they make no sense. So now I am in dilemma after I negated the argument. Is it the interpretation or is it the reference to a feeling that results in the promise making no sense?. Clearly the argument falls apart when I negate, hence its a necessary assumption.
(E) Promises that cannot be kept do not make any sense.
Eliminate. Argument says Reference : " and a promise to do something not within one’s control makes no sense."