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.

Which characteristic best identifies a pure substance?  
 (A) shape (B) texture (C) melting point (D) state of matter
C

Proxima Centauri is the closest star to the Sun. Which units do astronomers most often use for the distance between Earth and Proxima Centauri?  
 (A) miles (B) meters (C) light years (D) astronomical units
C

The chemical equation below shows reactants and products. 6CO_{2} + 12H_{2}O + light + enzymes -> C_{6}H_{12}O_{6} + 6O_{2} + 6H_{2}O Which statement is best supported by analyzing this equation?  
 (A) CO_{2} is made from the chemical reaction. (B) No new compounds are made from this reaction. (C) O_{2}, oxygen gas, is needed to make the reaction start. (D) The atoms rearrange in the chemical reaction so that C_{6}H_{12}O_{6}, glucose, is made.

D