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.

An organism's traits are largely determined by the genetic makeup of its parents. A mutation in which kinds of cells in a parent could cause a new trait to appear in the parent's offspring?
(A) sperm or egg (B) egg or nerve (C) nerve or muscle (D) muscle or sperm
A