Final answer:
The statement about IgM's VDJ sequence being the same regardless of its form (secreted or membrane-bound) is true, as the antigen-binding specificity remains constant.
Step-by-step explanation:
The statement that whether the IgM is secreted or it has it on its cell surface, the VDJ sequence is the same is true. Both the secreted form and the cell surface form of IgM have the same variable regions encoded by the V(D)J recombination process. For B-lymphocytes, the cell surface receptors are in fact membrane-bound immunoglobulins that comprise part of the B-cell receptor (BCR) complex. After encountering an antigen, some B cells will differentiate into plasma cells, which secrete the same immunoglobulin into the blood. Even though the secreted IgM is structurally different (as it becomes pentameric), the variable regions that determine antigen specificity are identical to the original membrane-bound monomeric form of IgM on naïve B cells.