Why does Angela think Frank is rejected from becoming an altar boy? (in book: Angela's Ashes)

A.
She ascribes it to class distinction and social prejudice.
B.
She insists that Frank did not know enough Latin.
C.
She thinks it is because Frank is too fragile and weak.
D.
She believes the clergy is trying to drive her and her children out of Ireland.
E.
She thinks Malachy’s reputation as an alcoholic has blighted Frank’s prospects.