When NPN transistor is used as an amplifier:

Explanation

In an NPN transistor used as an amplifier, the majority charge carriers are electrons, which flow from the N-type emitter into the P-type base and then proceed to the N-type collector. This movement is critical for the amplification process. Option A is correct because it describes the direction of electron flow correctly. Options B and D are incorrect as they describe the movement of holes, which are not the majority carriers in an NPN transistor. Option C is wrong because it incorrectly describes the direction of electron movement.