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: Some people carry a mutated allele of a particular gene that makes them resistant to HIV infection and AIDS. Which best describes this type of mutation?  
 (A) beneficial (B) asexual (C) harmful (D) unicellular
Example Output: A

Example Input: Water at 20°C in an uncovered pan is evaporating very slowly. What could be done to the water to make it evaporate more quickly?  
 (A) Cover it. (B) Heat it. (C) Place it in the dark. (D) Put salt in it.
Example Output: B

Example Input: After mining removes layers of rock from a hillside, new plants begin to grow in the cracks of the bare rock. The plants beginning to grow are an example of which natural process?  
 (A) secondary succession in an existing ecosystem (B) new species developing in an ecosystem (C) species competition in a community (D) primary succession in a new habitat
Example Output:
D