Instructions: 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.
Input: A crop of corn plants is genetically modified so that the plants produce a natural pesticide. People are concerned that these corn plants might transfer modified genetic material to other plants. Which of the following is the best way to further modify the plants to prevent them from transferring their genetic materials to other plants?
(A) changing the plants so they do not make pollen (B) changing the plants so they do not harm insects (C) changing the plants so they cannot produce nutrients (D) changing the plants so they cannot be easily identified
Output:
A