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.
Q: Which statement describes the formation of a delta?
(A) A large mass of ice and snow accumulates. (B) A mound of sand is built by wind. (C) A low area of land is surrounded by mountains. (D) A mass of sediment is deposited at the mouth of a river.
A:
D