The Phenomenal Diversity of Antibodies Produced by an Individual Is

The phenomenal diversity of antibodies produced by an individual is possible because

A) B-cells contain more genes than other cells of the body.
B) once the gene encoding an antibody is transcribed, the mRNA is sloppily translated, in effect introducing mutations (and therefore diversity) post-translationally.
C) even though they have the same number of genes as other cells of the body, virtually all of their genome is dedicated to antibody genes.
D) the gene fragments encoding antibodies are cut, reshuffled and spliced during a B-cell's development, enabling innumerable amino acid sequences to be generated.
E) None of these.