Even Though There Are More Protons in the Intermembrane Space

Multiple Choice

Even though there are more protons in the intermembrane space of the mitochondria, protons do not diffuse from there into the matrix.Why not?

A) The inner mitochondrial membrane is not permeable to them.
B) This would require energy.
C) Only water diffuses, not protons.
D) They are not charged.
E) Actually, they do diffuse.