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 Input:
Carolina uses a microscope to view a soil sample taken from her backyard. Which part of the soil would she ONLY be able to see with a microscope?  
 (A) bacteria (B) grass (C) rainwater (D) rocks

Ex Output:
A


Ex Input:
Evidence of organisms that lived on Earth a long time ago would most likely be found in  
 (A) crystals. (B) lava. (C) sedimentary rock. (D) metamorphic rock.

Ex Output:
C


Ex Input:
Of the following types of cells, which has the highest concentration of mitochondria?  
 (A) bone (B) muscle (C) nerve (D) skin

Ex Output:

B