Does the mitochondrial matrix ever run out of protons for pumping in oxidative phosphorylation?

1. Which of the following processes generates the most ATP? (Account for the no. of ATP)

a. ) Citric Acid Cycle

b.) Fatty Acid oxidation

c.) Glycogenolysis

d.) Glycolysis

e.) Pentose phosphate pathway

2. Does the mitochondrial matrix ever run out of protons for pumping in oxidative phosphorylation?