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: In a lab investigation, a student notes that two metal blocks have the same mass. Based on this observation, if the two blocks were put on opposite sides of a balance, they would best represent  
 (A) balanced forces. (B) unbalanced forces. (C) equal and opposite reactions. (D) objects in motion.

Answer: A


Question: 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

Answer: A


Question: Students go on a field trip to observe salmon spawning in a river. For safety reasons, the students should not  
 (A) explore alone. (B) listen to instructions. (C) take notes. (D) bring water.

Answer:
A