Respuesta :
The study of a living being is called biology.
The correct answer is A.
A system that is responsible for protecting the body from the alien pathogen that causes the disease to the human is called the immune system.
The first line of defense is the protective barrier of the body which prevent the entry of pathogen.
The T cells are the cells that help to make the antibodies to fight against the pathogen.
Hence, the correct answer is A that is T- Cells.
For more information, refer to the link:-
https://brainly.com/question/13899929
