Why Does a Phospholipid on the Cytoplasmic Side of the Cell

Multiple Choice

Why does a phospholipid on the cytoplasmic side of the cell membrane rarely flip to the extracellular side if both environments are polar?

A) The polar head group cannot pass through the nonpolar interior.
B) The two sides have different functions and thus the phospholipid would not function properly.
C) The cytoplasmic phospholipid is too big to pass through the membrane.
D) The cholesterol does not allow lipids to move.