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.

The trait for flower color is highly variable among certain species of rose plants, leading to the formation of flowers of different colors. How did the flower color variation in rose plants come about?
(A) through mutation (B) through pollination (C) through natural selection (D) through asexual reproduction
A