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:
Use of nuclear fuel would most likely reduce human contributions to which environmental problem?  
 (A) ozone thinning (B) landfill creation (C) shoreline erosion (D) greenhouse heating

Ex Output:
D


Ex Input:
Which difference between water and ice results in ice floating on cold water?  
 (A) heat (B) shape (C) density (D) volume

Ex Output:
C


Ex Input:
Which of the following is a harmful waste material that leaves the blood and travels through the lungs before leaving the body?  
 (A) CO2. (B) O2. (C) H2O. (D) NaCl.

Ex Output:

A