Answer: Option D
Antigen is a given substance that stimulates a specific immune system.
Explanation:
Antigen is a substance that can stimulate an immune response by activating lymphocytes (white blood cells) which acts as body defence against infections. Antigen is divided into two which are,
1. Foreign antigen or heteroantigen which is a foreign substance that stimulates immune response.
2. Autoantigen self antigen is a substance in the body that stimulates immune response.
