Why Is It That Dark Adaptation Takes Longer to Occur

Why is it that dark adaptation takes longer to occur than light adaptation?

A) in dark adaptation, it takes 15 minutes for the rods to adapt
B) in light adaptation, cones become active very quickly, typically in about 5 minutes
C) light adaptation makes use of bipolar cells while dark adaptation makes use of the ganglion cells
D) there is no difference between dark adaptation and light adaptation; they occur at the same rate