Which of the following statements) is/are correct? (i) Antigen is usually a foreign body which causes the formation of antibody. (ii) Antibody is a protein molecule. (iii) Antigen can be either protein o polysaccharide molecule. (iv) Antibody joins an antigen to destroy the latter.

• A. (i) and (ii)
• B. (i) and (iii)
• C. All are incorrect                         
• D. All are correct