Stupid question I think which lures you into choosing 'A' if indeed 'D' is the correct answer.
If you read at as a hypothetical scenario whereby you are in an established climb at Vy-30 knots and then you gain an acceleration and are still in an ESTABLISHED climb having accelerated then any acceleration is initially going to take you closer to Vy and improve the rate.
If you read it more literally and imagine that you are established in the climb at Vy-330 knots and then you start your acceleration by pitching forward for example to accelerate in level flight, then obviously your rate reduces until you restablish in the climb at the new speed.