instruction:
You are given a science question (hard-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 statement is an opinion about the element copper?  
 (A) Copper is a good conductor of electricity. (B) Copper mixed with silver is expensive. (C) Copper can be pounded into many shapes. (D) Copper is an excellent conductor of heat.
answer:
B


question:
What occurs if the body's renal system fails to work?  
 (A) Gas exchange is impaired. (B) Blood oxygenation no longer occurs. (C) Metabolic waste builds up in the blood. (D) Nutrients are no longer transported to organs.
answer:
C


question:
Gas and oil come from deposits of petroleum deep within the earth. What caused these deposits to form?  
 (A) Rocks were dissolved by water. (B) Lava deposited and then cooled. (C) The remains of plants and animals were trapped. (D) Air, water, and minerals combined.
answer:

C