Giving out all of my points, before i delete my account.
what is chemotherapy?

Chemotherapy is the use of any drug to treat any disease.

Explanation:

But to most people, the wordchemotherapy means drugs used for cancer treatment. It's often shortened to “chemo.” Surgery and radiation therapy remove, kill, or damage cancer cells in a certain area, but chemo can work throughout the whole body

answer; i do believe that the correct answer is ( portal of exit in the chain of transmission); good luck