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]: A leaf is covered in mud during a landslide. After one million years, this leaf will most likely be ___.  
 (A) a fossil (B) an animal species (C) a new plant species (D) a nonrenewable fuel
[EX A]: A

[EX Q]: Electron transport in mitochondria results in a chemiosmotic gradient of which particle across the mitochondrial membrane?  
 (A) ADP (B) ATP (C) protons (D) neutrons
[EX A]: C

[EX Q]: A "light year" refers to  
 (A) the distance light travels in one year. (B) the of time it takes light to travel from Earth to the Sun. (C) the amount of light required on Earth in one year. (D) the distance between two sources of light.
[EX A]:
A