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.

[Q]: Which characteristic property indicates that igneous rock cools slowly?  
 (A) mineral composition (B) hardness (C) density (D) crystal size
[A]: D


[Q]: As the molecules of water begin to slow down they go into a phase where they are no longer able to easily move past each other. The water is passing through a phase change and will     
 (A) remain a mixture. (B) remain a compound. (C) become an element. (D) become a compound.
[A]: B


[Q]: A pharmaceutical company has published the results of a limited experiment investigating the protective value of a chemical compound against high doses of UV rays on skin cells. It was later discovered that the results were not reproducible. What action could the company researchers have taken to avoid publishing erroneous results?  
 (A) Perform multiple trials. (B) Use only low levels of radiation. (C) Use different wavelengths of radiation. (D) Look into results of similar experiments before forming a hypothesis.
[A]:
A