If a patient with membranous nephropathy shows clinical improvement after induction therapy, what should be the next step in management?

A) Continue the same induction therapy indefinitely.
B) Gradually taper and discontinue induction therapy.
C) Switch to a different class of immunosuppressive agents.
D) Perform a renal biopsy to reassess disease activity.
E) Start maintenance therapy with a lower-dose immunosuppressant