instruction:
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.
question:
A tropical rain forest contains many tall trees. Smaller plants with large leaves grow at the base of the tall trees. The large leaves are most likely an adaptation of the plant due to which condition?  
 (A) lack of sunlight (B) lack of oxygen (C) lack of water (D) lack of food
answer:
A


question:
An atom becomes an ion with a -1 charge because the atom  
 (A) gains one electron. (B) loses one electron. (C) gains one proton. (D) loses one proton.
answer:
A


question:
Many states require vehicles to be examined and to meet safety and pollution standards. What impact might vehicle inspections have on the environment?  
 (A) The environment will not be polluted. (B) The environment will become more polluted. (C) Fewer pollutants will be released by vehicles. (D) Fewer pollutants will be produced by older vehicles.
answer:

C