Which of the Following Mechanisms Contributes to the Change from B

Which of the following mechanisms contributes to the change from B cell production of membrane Ig to secreted Ig?

A) V(D) J recombinase-mediated deletion of the exon encoding the transmembrane domain
B) Alternative processing of primary RNA transcripts to remove the transmembrane domain and include a secretory tail piece
C) Increased vesicular exocytosis of intracellular stores of the secretory form of Ig
D) Switch recombinase-mediated recombination of the heavy chain locus to juxtapose the V(D) J segment with the exon encoding a secretory tail piece
E) Up-regulation of ectoenzymes that proteolytically cleave membrane Ig heavy chains just proximal to the membrane