Why Do Nausea and Vomiting Occur After Radiation Therapy to the Abdomen

Why do nausea and vomiting occur after radiation therapy to the abdomen?

A) Because the patient is receiving chemotherapy at the same time as the radiation therapy
B) Because the radiation is metabolized by the liver,which alters the intestinal mucosa
C) Because the cancer in the gastrointestinal tract causes these clinical manifestations
D) Because the intestinal mucosa is the most radiosensitive tissue and divides rapidly