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: On a field trip, a student holds a frog and reports that it has slippery skin. This is an example of  
 (A) a measurement (B) a prediction (C) an explanation (D) an observation

A: D
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Q: Which plant is grown for food?  
 (A) Rice (B) Tobacco (C) Orchid (D) Cotton

A: A
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Q: The Grand Canyon is an example of  
 (A) erosion. (B) deposition. (C) an earthquake. (D) volcanic activity.

A:
A
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