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 Q]: When a cup of water at room temperature is put in a freezer, the water's state of matter will change from  
 (A) liquid to gas (B) gas to liquid (C) liquid to solid (D) solid to liquid
[EX A]: C

[EX Q]: Which is the most important safety measure to follow when using an acid in a classroom laboratory?  
 (A) wearing protective clothing and goggles (B) keeping the window open (C) closing the door to the hall (D) using bright fluorescent lights
[EX A]: A

[EX Q]: Which of the following properties best describes a material's ability to resist scratching?  
 (A) weight (B) flexibility (C) length (D) hardness
[EX A]:
D