Given the task definition and input, reply with output. You are given a science question (hard-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.

A river erodes its banks for thousands of years, and deposits the eroded material at its mouth. What two landforms did the river make?
(A) a hill and a delta (B) a delta and a canyon (C) a canyon and a dune (D) a dune and a delta
B