Question

a single that can cause an organism to react is known as a

Answer 1

antigen as here it is written that it is a kind of thing that makes one to react . If it is only an organism then it will be a pathogen otherwise if it is not necessarily an organism than it may be an antigen . an antigen is a thing which causes it may be pollen grain or pathogen.An pathogen is a organism that causes a disease and ultimately causes the host to react