instruction:
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.
question:
Which body systems are most involved in the response when someone stubs his or her toe?  
 (A) nervous and muscle (B) muscle and endocrine (C) nervous and digestive (D) reproductive and circulatory
answer:
A


question:
Which best describes a characteristic of the jet stream?  
 (A) It forms a boundary between a cold air mass and a warm air mass. (B) It creates the high winds around the eye of a hurricane. (C) It forces the hot air along the equator to rise to areas in North America. (D) It causes high pressure air masses to rotate clockwise.
answer:
A


question:
A cricket population includes approximately the same number of black and light-brown crickets. Black crickets are easier for birds to locate and eat. Over time, the population begins to consist of only light-brown crickets. The change in the color of the cricket population is a result of   
 (A) limited resources. (B) natural selection. (C) geographic isolation. (D) climate change.
answer:

B