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.
--------
Question: Sharpening a pencil and tearing paper are examples of physical changes. Which statement describes why these are physical changes?  
 (A) There is a change in how the objects are used. (B) There is a change in the appearance of the objects. (C) There is a change in the materials from which the objects are made. (D) There is a change in both the appearance of the objects and the materials from which they are made.

Answer: B


Question: A class made a solar cooker out of a large can. What color should they paint the can in order to collect the most heat?  
 (A) black (B) green (C) pink (D) white

Answer: A


Question: Which gas is transported by the circulatory system in humans and is used by cells during respiration to release energy stored in food?  
 (A) carbon dioxide (B) nitrogen (C) hydrogen (D) oxygen

Answer:
D