In this task, you are given a multiple-choice question and you have to pick the correct option. Answer with option indexes (i.e., "A", "B", "C", and "D").

In what way are valleys formed? (A) the passage of water in a straight or winding path moving consistently (B) pools of water filling until a deep lake forms (C) rain water frequently raining down (D) high winds blowing rain and hail
A