You are given a science question (easy-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.
One example: Which part of a bicycle BEST moves in a circle?
(A) Seat (B) Frame (C) Foot pedal (D) Kickstand
Solution is here: C
Explanation: Seat, frame and Kickstand are static parts of the bicycle, even when bicycle moves. Foot pedal moves in a circle as bicycle moves.

Now, solve this: A small, fast-moving river in is in a V-shaped valley on the slope of a mountain. If you follow the river to where it passes through a plain, what will the river most likely look like compared with how it looked on the mountain?
(A) Much the same (B) Deeper and faster (C) Slower and wider (D) Straighter
Solution:
C