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.

Input: Consider Input: When manned space exploration began, NASA used the gravity assist concept so that spacecraft could conserve fuel. Which statement explains why the gravity assist concept was useful for spacecraft to successfully travel and return to Earth?  
 (A) It gave spacecraft a timed trajectory. (B) It ensured spacecraft would return home safely. (C) It was helpful in planning spacecraft trajectories. (D) It ensured spacecraft would avoid being pulled into the sun.

Output: C


Input: Consider Input: What is an environmental threat posed by oil and gas acquisition and transport that is not posed by the acquisition and transport of the energy resources uranium, and wood?  
 (A) habitat change (B) vehicle pollution (C) pipeline leaks (D) soil compaction and loss

Output: C


Input: Consider Input: In Alaska, there are fewer hours of daylight in the winter than in the summer. Which statement best explains why this difference occurs?  
 (A) The Sun burns hotter in the summer. (B) The Sun moves below the horizon in the summer. (C) The Northern Hemisphere is closer to the Sun in the winter. (D) The Northern Hemisphere is tilted away from the Sun in the winter.


Output: D