Which of the following sentences about the basic structure of Ab are correct?
A.
Ig is composed of four polypeptide chains joined by S-S bonds
B.
According to the differences of H chains (amino acid composition, sequence), Igs can be divided into 5 classes
C.
Five classes of Igs include IgG, IgA, IgM, IgD and IgE
D.
An IgG molecule contains variable region, constant region and hinge region