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]: What is the first step of the process in the formation of sedimentary rocks?  
 (A) erosion (B) deposition (C) compaction (D) cementation
[A]: A


[Q]: Sound is able to travel faster in solids than in air because the molecules in a solid are  
 (A) closer together than air molecules. (B) more easily moved than air molecules. (C) moving faster than air molecules. (D) larger than air molecules.
[A]: A


[Q]: Which of these elements is not likely to be found in an organic compound?  
 (A) carbon (B) hydrogen (C) nitrogen (D) potassium
[A]:
D