(c) : Glucose is the chief respiratory substrate which fields maximum number of ATP molecules. Glucose is the most common substate in glycolysis. Any other carbohydrate is first converted into glucose. During glycolysis it changes to pyruvic acid and net gain is of 2 ATP and 2 NADH, molecules. And later on during Krebs cycle 30 molecules of ATP are produced. So a total of 38 ATP molecules are produced from 1 mol of glucose during aerobic respiration.