TASK DEFINITION: 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.
PROBLEM: Many scientists think that burning fossil fuels has increased the amount of carbon dioxide in the atmosphere. What effect would the increase of carbon dioxide most likely have on the planet?  
 (A) a cooler climate (B) a warmer climate (C) lower relative humidity (D) more ozone in the atmosphere

SOLUTION: B

PROBLEM: The Moon lacks weather and climate changes like those on Earth. What causes the lack of weather on the Moon?  
 (A) the lack of water (B) the presence of igneous rock (C) the very thin atmosphere (D) the lack of magnetic poles

SOLUTION: C

PROBLEM: Emily is riding her bicycle. Which best explains why only some of the energy used to pedal her bicycle is transferred into forward motion of the bicycle?  
 (A) The energy of the bicycle tire is applied in a circular motion. (B) The energy of the bicycle is transferred to only one wheel. (C) The gears and chain of the bicycle are covered with oil. (D) The gears and chain of the bicycle generate friction.

SOLUTION:
D