Answer: D. Cancer
Cancer is when cells grow at an abnormal and uncontrolled rate.
The correct answer is (c) discover antigens in body fluids.
B lymphocytes act as antigen presenting cells that recognizes and displays the antigen to the white blood cells. These cells process the antigens that are present in body fluids. Professional antigen presenting cells includes B-lymphocytes, macrophages, dendritic cells, etc.
When organisms mate without human interference, it is called natural selection.
The fertilizers used by farmers can have negative effects on aquatic ecosystems because there is every possibility that the runoffs from the fields can create an algal bloom in the nearby water body. This algal bloom can have a very negative effect on the living organisms of the aquatic body. I hope it helps.
Passive diffusion is a form of passive transport and a type of diffusion by which particles from a high concentration gradient passes through a biological membrane to a low concentration gradient. Diffusion, or simple diffusion on the other hand, is the passage of molecules without the need of a membrane.