Instructions: 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.
Input: Gases can be easily compressed and are able to expand to fill their containers. These descriptions of gases are examples of  
 (A) changes in state. (B) states of matter. (C) properties of matter. (D) changes in properties.
Output:
C