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.

One role of a producer in a food chain is to provide  
 (A) water for plants (B) sunlight for plants (C) nutrients for animals (D) shelter for animals
C

A student tosses a ball into the air. Which force causes the ball to fall back to the ground?  
 (A) gravity (B) magnetism (C) mechanical (D) friction
A

Which cells help to destroy pathogens such as bacteria that enter the human body?  
 (A) red blood cells (B) liver cells (C) white blood cells (D) brain cells

C