In this subtask, you will answer a simple science question. Please indicate the correct answer. If you're not sure about the answer, choose the last option "I don't know". Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D', 'E'. The "A"-"D" responses correspond to the answer options mentioned in the input. There is a 5th option "E" which should be used for questions for which you're not sure about the answer (e.g., when the questions do not provide enough information to answer).

Example Input: Question: Gordon reads that if an object is closer to the center of a planet, then the force of gravity will be stronger. According to this information, where would the force of gravity be the strongest? (A) in a flying airplane (B) on a tall mountain (C) in a deep valley (D) on an islan?
Example Output: C.

Example Input: Question: Which system is responsible for getting rid of chemical waste and water? (A) digestive (B) urinary (C) locomotion (D) circulator?
Example Output: B.

Example Input: Question: Which example best shows structures that make up the digestive system in the human body? (A) heart, blood, vessels (B) nose, trachea, lungs (C) brain, spinal cord, nerves (D) esophagus, stomach, intestine?
Example Output:
D.