The Energy Yield of Any Energy-Transforming Pathway

The energy yield of any energy-transforming pathway

A) is always fixed, despite the removal of precursor metabolites for biosynthesis.
B) is variable depending on the type of enzymes used.
C) is variable depending on the amount of precursor metabolites removed for biosynthesis.
D) is fixed by the amount of oxygen available.
E) is fixed by the amount of carbon dioxide available.