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 of these determines whether a fertilized egg develops into a toad, a snake, or a lizard?  
 (A) the sex of the egg (B) the age of the egg (C) the size of the egg (D) the genes of the egg

A: D
****
Q: How many basic units of information in a DNA molecule are required to encode a single amino acid?  
 (A) 1 (B) 2 (C) 3 (D) 4

A: C
****
Q: How many atoms are in one formula unit of magnesium hydroxide, Mg(OH)_{2}?  
 (A) 6 (B) 5 (C) 4 (D) 3

A:
B
****