Answer:
Tomorrow
Explanation:
The one-word answer to this simple riddle is 'Tomorrow'. Tomorrow never comes, but people always push back their plans and say that they will "do it tomorrow". So tomorrow is always coming but it never actually arrives.
(i'm gonna try to give more reason cause my last comment was deleted)
i think it may be D because that would be the only one to make sense
it wouldn't be A because how would changing their behavior help physical impairments? (it wouldn't)
i don't think it would be B because how could that help..
i don't think it would be C because medication does not help with those kinds of problems, i think,
hope this helps :)
sorry if im wrong :(