TASK DEFINITION: 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.
PROBLEM: Rocks are classified as igneous, metamorphic, or sedimentary according to  
 (A) their color (B) their shape (C) how they formed (D) the minerals they contain

SOLUTION: C

PROBLEM: Which of the following is the most likely cause of earthquakes?  
 (A) shifting rock layers (B) crashing meteorites (C) rotation of the core (D) magnetic force

SOLUTION: A

PROBLEM: Before large trees could grow on Earth, what had to happen first?  
 (A) Rocks were eroded to form soil. (B) Molten rock warmed Earth's interior. (C) Earth's gravity accumulated to modern levels. (D) Volcanoes exploded to form mountaintop lakes.

SOLUTION:
A