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]: A student has just completed a laboratory activity. What is the last action that the student should perform before leaving the lab area?  
 (A) wash hands (B) turn off all equipment (C) put away all glassware (D) wash instruments and table tops
[EX A]: A

[EX Q]: Which pair would be most necessary for life to develop on another planet?  
 (A) sulfur and nitrogen (B) helium and hydrogen (C) liquid water and carbon (D) chlorophyll and oxygen
[EX A]:
C