Part 1. Definition
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.
Part 2. Example
Which part of a bicycle BEST moves in a circle? 
 (A) Seat (B) Frame (C) Foot pedal (D) Kickstand
Answer: C
Explanation: Seat, frame and Kickstand are static parts of the bicycle, even when bicycle moves. Foot pedal moves in a circle as bicycle moves.
Part 3. Exercise
Individuals that carry a particular allele may have more descendants than other individuals, resulting in the allele becoming more common. Which process causes random alleles to become more common within a population?  
 (A) gene shuffling (B) directional selection (C) natural selection (D) genetic drift
Answer:
D