instruction:
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:
Which of these is a structure that is present in all organisms?  
 (A) a tissue (B) a cell (C) a stomach (D) a brain
answer:
B


question:
Which of these substances is correctly identified as a mineral?  
 (A) coal (B) quartz (C) granite (D) sandstone
answer:
B


question:
Acid rain is the result of pollutants being released into the  
 (A) air. (B) soil. (C) rivers. (D) oceans.
answer:

A