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:
Patricia and her classmates are visiting different rocky areas in the city. They want to know what kind of rocks can be found in each area. If the investigation is done correctly, what will Patricia and her classmates do each time they visit an area?  
 (A) draw the rock shapes (B) count the rock numbers (C) record the rock types and locations (D) measure the rock masses and lengths

Ex Output:
C


Ex Input:
Plants growing in a pond release a gas that fish need to survive. Which gas do the plants release that fish use?  
 (A) helium (B) hydrogen (C) nitrogen (D) oxygen

Ex Output:
D


Ex Input:
The tendency of an element to react chemically is closely related to  
 (A) the number of valence electrons. (B) the ratio of protons to neutrons. (C) how tightly atoms are packed. (D) the number of neutrons in atoms.

Ex Output:

A