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) They do not diffuse because the inner mitochondrial membrane is not permeable to them.
B) They do not diffuse because that would require energy.
C) They do not diffuse because only water diffuses, not protons.
D) They do not diffuse because they are not charged.
E) Actually, they do diffuse.