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.

Q: What is the function of the nucleus in a cell?  
 (A) provides energy (B) provides nutrients (C) controls activity (D) controls movement

A: C
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Q: How is xylem similar to phloem in a plant?  
 (A) They both take in water from the soil. (B) They both transport materials through the plant. (C) They both make sugar in the leaves. (D) They both store waste products in the plant cells.

A: B
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Q: What process is most responsible for the extinction of most species of plants and animals that have lived on Earth?  
 (A) gene mutation (B) environmental changes (C) selective breeding (D) decrease in reproduction

A:
B
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