The answer is Cp53.

Mutations of the p53 gene are associated with malignancies, and research suggests that the mutation may increase the risk of chemotherapy resistance.  

A is not correct because NRAS mutations play a role in the development of a variety of cancers and most notably increase the risk of breast and ovarian cancer. However, the mutation has not shown to positively or negatively affect response to chemotherapy.  

is not correct because APC gene mutations increase the likelihood of developing colorectal cancer but have not shown any effect on chemotherapy response. 

D is not correct because the presence of a mutation to the VHL (Von-Hippel-Landau) gene will allow abnormal cell growth and division, leading to remarkably higher cancer rates, but has not demonstrated a significant impact on response to treatment.