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.

Example Input: When nitrogen-rich runoff from farms enters a nearby farm, it causes abundant growth of algal mat on the pond surface. As a result, underwater plants in the pond begin to die. Identify the limiting factor that is most responsible for causing the underwater plants to die.
(A) oxygen (B) sunlight (C) nitrogen (D) carbon dioxide
Example Output: B

Example Input: Fertilizers added by farmers to the soil contain high amounts of nitrates. How do fertilizers affect the nitrogen cycle?
(A) More nitrates are available for plants to absorb. (B) More nitrates are available for animals to eat. (C) More nitrogen gas is released into the atmosphere. (D) More nitrogen is converted by bacteria into nitrates.
Example Output: A

Example Input: When buying a sunscreen, which is the best question to keep in mind while reading the label for maximum effectiveness?
(A) What is the cost per ounce? (B) Who is the manufacturer? (C) Is the product waterproof? (D) How much protection does it provide?
Example Output:
D