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.
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Question: Wolves have adapted skills for hunting large hoofed animals such as elk, deer, or moose. Wolves tend to target prey animals that are sick or weak. The wolf benefits from this strategy because it uses less energy to hunt. How would the prey animal population also benefit from this strategy?  
 (A) by promoting detrimental genes (B) by stimulating beneficial DNA mutations (C) by preventing the introduction of other predator species (D) by increasing the reproductive success of healthy prey animals

Answer: D


Question: Which of these is a structure that is present in all organisms?  
 (A) a tissue (B) a cell (C) a stomach (D) a brain

Answer: B


Question: How do the circulatory system and the respiratory system depend on one another?  
 (A) Oxygen collected by the respiratory system is carried throughout the body by the circulatory system. (B) Solid wastes collected by the circulatory system are carried throughout the body by the respiratory system. (C) Nutrients collected by the respiratory system are carried throughout the body by the circulatory system. (D) Carbon dioxide collected by the circulatory system is carried throughout the body by the respiratory system.

Answer:
A