Which antibody has maximum concentration in GI secretions: (A) IgG, (B) IgM, (C) IgA, (D) IgD
Answer is C. IgA antibody

It is the second most abundant antibody (after IgG).
It is major immunoglubulin in clostrum, saliva, tears, respiratory and gastrointestinal secretions.
IgA occurs in two forms.