What Was the Initial Explanation for the Sensitivity of Cancer

What was the initial explanation for the sensitivity of cancer cells to radiation therapy and chemotherapy as compared to normal cells?

A) Cancer cells are sensitive to radiation and chemotherapy because they divide more rapidly.
B) Cancer cells are less resistant to drugs or radiation because once they sustain genetic damage,they either progress through the cell cycle while repair is incomplete and they may undergo apoptosis.
C) Cancer cells are sensitive to radiation and chemotherapy because they divide more slowly.
D) Cancer cells are less resistant to drugs or radiation because once they sustain genetic damage,they either arrest the cell cycle until repair is complete or undergo apoptosis.
E) Cancer cells are sensitive to radiation and chemotherapy because they will not undergo apoptosis.