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.

[EX 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.
[EX A]: A

[EX Q]: Scientists found a new species of a complex organism at the bottom of the ocean. The organism most likely
(A) is unicellular. (B) is a form of bacteria. (C) is made of multiple cells. (D) lacks an organized nucleus.
[EX A]: C

[EX Q]: In the spring and early summer, bears often scratch their backs against trees to remove winter fur. This is an example of an animal
(A) completing its life cycle (B) beginning hibernation (C) responding to its environment (D) preparing for migration
[EX A]:
C