The Inner Membranes of Both Mitochondria and Chloroplasts Are Folded

The inner membranes of both mitochondria and chloroplasts are folded into various arrangements. What is the advantage of having a folded membrane, rather than a simple interior membrane that follows the same oval shape as the exterior membrane?

A) The folds in the membranes are a physical barrier for compounds that attempt to enter the organelle.
B) The folds allow for more surface area for the chemical reactions that occur across the inner membranes.
C) The folds allow these organelles to interact more efficiently with Golgi bodies.
D) The folds cause a necessary change in the organelles' internal pH.