Answer: Five.
- A Five
- B Two
- C Ten
- D Twenty
Correct answer: A. Five
Explanation: There are five antibody classes: IgG, IgA, IgM, IgE and IgD.
An antibody is Y-shaped, with two identical antigen-binding sites at the tips of the variable regions - each shaped to recognise one specific antigen - while the constant (Fc) region at the base is recognised by immune cells to trigger further responses.
Concept context
Innate and adaptive immunity, B cells, T cells, antibodies, vaccines, and immune disorders. Critical for NEET.