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.

When animals use energy, they produce  
 (A) nitrogen (B) iron sulfide (C) oxygen (D) carbon dioxide
D

What season is the Northern Hemisphere experiencing when it is tilted away from the Sun?  
 (A) spring (B) summer (C) autumn (D) winter
D

What major events cause islands to form in the Pacific Ocean?  
 (A) tsunamis (B) severe storms (C) volcanic eruptions (D) erosion

C