You are given a science question (hard-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 Q]: A main function of a plant's seed is to  
 (A) store food to be used during early development (B) attract pollen to be used during development (C) take in light energy to be used during photosynthesis (D) produce chlorophyll to be used during photosynthesis
[EX A]: A

[EX Q]: Water freezing is an example of a  
 (A) liquid changing to a solid (B) solid changing to a liquid (C) gas changing to a solid (D) gas changing to a liquid
[EX A]: A

[EX Q]: An old T-shirt can be ripped into smaller pieces and used as rags. An empty milk jug can be used to water houseplants. Both of these are examples of how  
 (A) saving water conserves future resources (B) using old materials can waste money (C) plants need water to be healthy (D) everyday materials can be reused
[EX A]:
D