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.

Example Input: A student plans to design a new toothpaste tube that will give the same amount of toothpaste every time it is squeezed. Which should the student do first when designing the new tube?  
 (A) make a data table of amounts of toothpaste (B) gather building materials (C) create models of old toothpaste tubes (D) draw a few possible solutions
Example Output: D

Example Input: 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.
Example Output: B

Example Input: A scientist was digging for dinosaur bones in a dry river bed. It started to rain and the scientist had to leave the area. If another scientist wanted to continue digging in the same place, he would have to  
 (A) know how deep the river got when it rained. (B) know how far the river bed is from a town. (C) have accurate notes describing the location. (D) have the weather records for the past few months.
Example Output:
C