There is confusion and ambiguity since the right answer changes depending on the assumed timescale. Would have been nice if they specified.
If the question is about the immediate response (the first few seconds) then you're pushing the nose down, which will of course lower both your climb rate and climb gradient (aka angle) no matter what, and the right answer is D.
If the question is about the new stabilized condition where the speed has settled at its new value, and the attitude is raised to whatever will hold that speed (say, 30+ seconds in the future) then A and B are both right.
For answering a standardized test of course you can't go up to the proctor and ask for more detail about the unstated background, all you can do is pick one of the 4 answers. Fortunately, in most testing formats, there can only be one right answer. That means it can't be both A and B, so I'd pick D.
More important is the actual flying application of this ambiguity. With any elevator input, you always have to think both about the short-term response, and the longer-term new energy state. Failing to do this gets every student in trouble when they find themselves a little low on short final, and don't have as much mental room to consider everything. They only think of the naive and simplistic response: to pull back on the elevator. This pulls the nose up, and shallows out the descent, but only for a few seconds. Then we're below best glide speed, with more total drag, and the plane starts descending even steeper.
Trouble is, that the response over the first few seconds, (a shallower flight path) reinforces the student's incorrect view of elevator control inputs (that the airplane goes where you point the nose), he sees that and thinks "job well done" and goes onto the 50 other tasks that are simultaneously overloading him. When he sees that the plane is coming down steeper, if he's bright, he'll do the right thing for his energy state and give it some power; if not, he'll pull the nose up even higher, slow the plane even more, thereby adding even more drag, and increasing the ultimate sink rate even more. If he's really bright, then on his next approach, he'll give it power instead of elevator the first time he sees himself getting low!
Or if he flies a plane with autothrottles he can forget about all this nerd junk and just fly the airplane around by pointing the nose like a video game. Then when there's a breakdown in some part of the total system, become the next Asiana 214 or Pinnacle 3701 because he doesn't understand how airplanes fly.
Last edited by Vessbot; 28th May 2017 at 18:17.