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.

[Q]: A student is trying to identify a mineral that has a nonmetallic luster and is black. It can also be scratched with a fingernail. According to the mineral reference sheet, the unidentified mineral is most likely  
 (A) mica. (B) magnetite. (C) hornblende. (D) quartz.
[A]: A


[Q]: How much time is required for a bicycle to travel a distance of 100 m at an average speed of 2 m/s?  
 (A) 0.02 s (B) 50 s (C) 100 s (D) 200 s
[A]: B


[Q]: Sean felt the room become cooler. His body adjusts to enable him to survive. Which response did Sean have that enabled his body to continue to function correctly?  
 (A) an increase in cellular respiration which increases heat production (B) sweating from the skin to lower inner heat levels (C) opening of the capillaries in the skin to obtain more heat (D) an increase in the metabolism which decreases heat from cells
[A]:
A