TASK DEFINITION: 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.
PROBLEM: In the human body, which system functions primarily to defend the body against disease?  
 (A) digestive (B) immune (C) nervous (D) respiratory

SOLUTION: B

PROBLEM: Spring tides occur during which lunar phases?  
 (A) first quarter and last quarter (B) full moon and new moon (C) when the moon is waxing (D) when the moon is waning

SOLUTION: B

PROBLEM: Which process is common to most living things?  
 (A) flying (B) talking (C) seeing (D) reproducing

SOLUTION:
D