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: When oxygen combines with hydrogen, which substance is formed?  
 (A) water (B) vinegar (C) hydrochloric acid (D) hydrogen dioxide

SOLUTION: A

PROBLEM: Which of these occurs if myosin fails to bind to actin during muscle contraction?  
 (A) The muscle cells will lose ATP. (B) The muscle cells will remain relaxed. (C) The muscle cells will produce lactic acid. (D) The muscle cells will lose calcium ions.

SOLUTION: B

PROBLEM: The danger posed to fish in an aquarium by an overpopulation of bacteria caused by an algal bloom is most likely a  
 (A) decrease in water temperature. (B) reduction in oxygen levels. (C) decrease in food supply. (D) removal of minerals.

SOLUTION:
B