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]: Two pieces of the same metal are placed on a table. The pieces of metal have the same density, mass, and texture. Which characteristic must be the ONLY difference between the two samples?  
 (A) They have different dimensions. (B) They have different boiling points. (C) They are made up of a different type of matter. (D) They contain a different amount of matter per unit volume.
[A]: A


[Q]: Black fur is dominant to white fur in guinea pigs. If two black guinea pigs (Bb) are crossed, what color will the fur of their offspring be?  
 (A) 100% black (B) 100% white (C) 50% black, 50% white (D) 75% black, 25% white
[A]: D


[Q]: Which of these is a function of all cells?  
 (A) to produce oxygen through photosynthesis (B) to combine with other cells to form tissues (C) to subdivide to form cells for sexual reproduction (D) to transfer genetic information from one generation to the next
[A]:
D