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.

Input: Consider Input: A student conducts an investigation. In order to make a valid conclusion, she must  
 (A) have a testable hypothesis. (B) place the data in a graph. (C) use the best technology. (D) test multiple variables.

Output: A


Input: Consider Input: Which material is the best conductor of electricity?  
 (A) Wood (B) Metal (C) Stone (D) Plastic

Output: B


Input: Consider Input: What should be added to soil to increase its water retention?  
 (A) pebbles (B) sand (C) rocks (D) clay


Output: D