29. While other nucleoside triphosphates (NTPs), such as TTP, CTP, and GTP exist within cells, ATP is the primary energy currency. Which of the following explains why ATP is favored in this role? (A) ATP has a unique chemical structure that allows it to store significantly more energy per phosphate bond than other NTPs do. (B) ATP is the most abundant NTP in cells, making it readily available for energy-intensive processes. (C) ATP hydrolysis releases an optimal amount of energy that is sufficient to drive most cellular reactions, but not so much that energy is wasted as heat. (D) ATP is the only NTP that can be readily synthesized from ADP through both substrate-level and oxidative phosphorylation. (E) ATP has a higher affinity for energy-coupling enzymes than other NTPs, making it a more efficient energy donor.