Correct Answer: B
Explanation:
Sol. An antigen is usually a foreign protein molecule (in some cases it is a polysaccharide) which enters the body fluids of an animal as part of an infectious agent and is capable of inducing the production of specific antibodies. An antibody is a molecule produced by animals in response to antigen and has the particular property of combining specifically with the antigen which induced its formation. It is a blood protein (globulin) which may make an infected animal immune to a foreign antigen. This response is called the immune response.