Which of the Following Best Describes the Function of Tapasin

Which of the following best describes the function of tapasin?

A) Tapasin is an antagonist of HLA-DM and causes more significant increases in MHC class I than MHC class II on the cell surface.
B) Tapasin is a lectin that binds to sugar residues on MHC class I molecules,T-cell receptors,and immunoglobulins and retains them in the ER until their subunits have adopted the correct conformation.
C) Tapasin is a thiol-reductase that protects the disulfide bonds of MHC class I molecules.
D) Tapasin participates in peptide editing by trimming the amino terminus of peptides to ensure that the fit between peptide and MHC class II molecules is appropriate.
E) Tapasin is a bridging protein that binds to both TAP and MHC class I molecules and facilitates the selection of peptides that bind tightly to MHC class I molecules.