Answer:
a. antigen
Explanation:
The Immune system is composed of immune cells that defend the body against foreign substances such as bacteria or virus. Lymphocytes (B and T cells) are one of the main immune cells
Lymphocytes have the ability to recognize and bind to antigens, wich are substances foreign to the body ( i.e bacterial or virus elements) that evokes an immune response.
the lightest radiation is Aron.
Petrochemicals include many things, I would say All of the above. Hope this helped! :)
Different = Heterozygous ex. Aa
