Rodents who experienced inescapable shocks were more prone to developing cancer if they had previously been exposed to:.
a) natural killer cells.
b) serotonin.
c) T lymphocytes.
d) macrophages.
e) carcinogens.

E. Carcinogen

Explanation: The formation of cancer is often termed as carcinogenesis. Carcinogenesis is caused by carcinogens which can be a substances in air, radiation which could cause carcinogenesis, carcinogens may also be used to describe factors such as environmental, chemical or etiquettes which could result in the formation of carcinogenic cells.

Hence, carcinogen is any sort of substance or condition that can directly result to cancer. It could be a chemical substance, a virus, or medications and radiation used in the treatment of cancer.

answer; ///attempts to change more than once behavior at the same time;