instruction:
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).
question:
Question: The systems of the human body work together. Which system works with the skeletal system by pulling on the bones to create movement?  (A) digestive (B) circulatory (C) muscular (D) nervou?
answer:
C.


question:
Question: Fourth graders are planning a roller-skate race. Which surface would be the best for this race?  (A) gravel (B) sand (C) blacktop (D) grass?
answer:
C.


question:
Question: Which term best describes the moon?  (A) the moon orbits the sun (B) The moon is a satellite of the Earth (C) The moon gives off its own light (D) the moon orbits the Earth once a yea?
answer:

B.