Answer: Option (B) is the correct answer.
Step-by-step explanation:
Direct current is a current which flows in one direction, that is, flow of electrons is only in one direction.
Whereas alternate current is a current which reverses periodically, that is, there will be change in direction of electrons after a period of time.
Thus, we can conclude that the statement, In DC, electrons move in only one direction. In AC, electrons move in one direction and then in the other direction defines AC and DC correctly.