Which of the following describes the structure of the B-cell receptor?

A) It is a type I trans-membrane protein.
B) It is a type II trans-membrane protein.
C) It is a membrane bound form of an antibody molecule.
D) It is composed of two polypeptides, one of which has a trans-membrane domain.
E) It is composed of two polypeptides, both of which contain trans-membrane domains.