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]: Which example would result in new cells that are most different from the parent cells?  
 (A) yeast cells splitting into new cells (B) bacteria cells dividing into new cells (C) skin cells dividing to produce more skin cells (D) sperm and egg cells uniting to produce fertilized egg cells
[EX A]: D

[EX Q]: Oxygen reacts with iron to produce rust and with hydrogen to produce water. Which statement describes both reactions?  
 (A) A different mixture is formed in each case. (B) A different solution is formed in each case. (C) Both a change of state and of elements is involved. (D) New molecules are formed but the same elements exist.
[EX A]: D

[EX Q]: The number of stars in the Milky Way Galaxy is best estimated as  
 (A) one hundred thousand. (B) one hundred million. (C) one hundred billion. (D) one hundred trillion.
[EX A]:
C