At the NMJ, Postjunctional Folds Radiate into the Muscle Fiber

At the NMJ, postjunctional folds radiate into the muscle fiber from the cleft at
Regular intervals. What is their role at neuromuscular synapses?

A) Binding transmitter molecules
B) Increasing the postsynaptic surface area for receptors
C) Reducing the space between the presynaptic and postsynaptic cells
D) Increasing the space between presynaptic and postsynaptic cells
E) Degrading transmitter after binding to receptors