C.it changes DNA,but it is random
C is the correct answer because it is what that determines the gene
"An organism in which the two copies of the gene are identical — that is, have the same allele — is called homozygous for that gene. An organism which has two different alleles of the gene is called heterozygous."
The answer is S phase.
If drugs prevent DNA replication which occurs in the S phase. That means that the S phase will be affected by these drugs.
