A small amount of ATP is made in glycolysis by which of the following processes?

• A. Harnessing energy from the sun
• B. Transport of electrons through a series of carriers
• C. Transfer of electrons and hydrogen atoms to NAD⁺
• D. Attachment of a free inorganic phosphate (P_i) group to ADP to make ATP
• E. Transfer of a phosphate group from a fragment of glucose to ADP by substrate-level phosphorylation