Protective proteinous chemical compounds produed by the immune cells in response to antigens are called antibodies, also called immunoglobulins. There are five classes of antibodies: IgA, IgD, IgE, IgG and IgM. Following diagram is that of a specific class of antibodies. Observe the diagram and answer the questions listed below the diagram:
(i) To which class of antibodies, this antibody belongs to ?
(ii) Identify the parts of the diagram labelled as A and B.
(iii) Give the name of the part of antibody which binds the antigen.
(iv) Which type of immune system is formed by the antibodies?