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.
--------
Question: What is the primary function of white blood cells in humans?  
 (A) carry oxygen (B) fight disease (C) grow tissues (D) remove waste

Answer: B


Question: Which material best conducts heat and electricity?  
 (A) metal (B) plastic (C) rubber (D) wood

Answer: A


Question: Which factor would have the greatest influence on the southern migration of animals living in the Northern Hemisphere?  
 (A) strong storms (B) long periods of drought (C) cold air temperatures (D) increasing daylight hours

Answer:
C