B: The sequence of the DNA determines and individual's traits
A cannot be the answer because while there is a part of a DNA sequence that determines the sex of an individual, there is far more to it. C is not the answer because there isn't necessarily a code for mutations, it's something that happens. D is not the answer because someone's genes are set.
Question Two:
C: Meiosis
Fertilization is the process that occurs when a sperm cell meets an egg cell. Mitosis is how regular cells reproduce. Replication is when DNA reproduces. Therefore, the answer is Meiosis.