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.

[EX Q]: The cheetah population around the world has decreased because of poaching and loss of habitat. The surviving population is found to have similar alleles. Which factor is endangering the species' survival the most?  
 (A) harmful genetic mutations (B) shrinking of the gene pool (C) decrease in competition (D) increase in adaptations
[EX A]: B

[EX Q]: Which of these substances is correctly identified as a mineral?  
 (A) coal (B) quartz (C) granite (D) sandstone
[EX A]: B

[EX Q]: The Hardy-Weinberg law is only valid when  
 (A) the population is small. (B) migration into the population is occurring. (C) immigration into the population is occurring. (D) the population is large.
[EX A]:
D