When fertilization occurs, the resulting zygote is a diploid cell containing two of every type of chromosome. This is because one of each type of chromosome is – a
deleted during the fertilization process
b
duplicated within sperm cells
c
mutated by ultraviolet radiation
d
contributed by both parents

d  contributed by both parents

Explanation:

The zygote is formed by the fusion of two gametes (the sperm and the egg). Each gamete is haploid, which means it contains one copy of every chromosome.

When the gametes fuse during fertilization, the diploid state is restored, and the zygote has two copies of every chromosome - one from the mother and one from the father.