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: Which statement explains why a mother's unhealthy diet during pregnancy is harmful to her embryo's development?  
 (A) The embryo inherits half its chromosomes from its mother. (B) The embryo receives its food from its mother through the placenta. (C) The embryo receives oxygen through the placenta. (D) The embryo receives mutations carried by its mother.

A: B
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Q: About how long is a lunar cycle?  
 (A) 1 day (B) 1 week (C) 28 days (D) 52 weeks

A: C
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Q: In the 17th century, Gregor Mendel crossed pea plants with different traits and observed the results in their offspring. To which of these did Mendel contribute most directly with his work?  
 (A) medicine (B) agriculture (C) science of force and motion (D) science of heredity and variation

A:
D
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