Fact 1: Plasma cells are activated B cells that secrete antibodies.

Fact 2: Antibodies are manufactured by the immune system.

Given the two facts above, answer the question "The molecules secreted by activated B cells are part of the:" with the following options: 
- immune system
 - Organic compounds
 - Energy.
 - an organism's body
 - acetic acid
 - harmful substances
 - Chemical energy
 - Veins and arteries.


 

 immune system        