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.

[EX Q]: Which of these substances is correctly identified as a mineral?  
 (A) coal (B) quartz (C) granite (D) sandstone
[EX A]: B

[EX Q]: Shale is a sedimentary rock that can be metamorphosed into slate by  
 (A) cementation. (B) chemical weathering. (C) sedimentation. (D) increased pressure.
[EX A]: D

[EX Q]: What is the most likely effect of a drought on a population of frogs that live in a shallow swamp?  
 (A) only younger frogs will survive (B) the number of predators will increase (C) decrease in frog population as water evaporates (D) increase in frog population as more land is exposed
[EX A]:
C