Why does fusion of light nuclei release energy per nucleon more efficiently than fission of heavy nuclei?

Why does fusion of light nuclei release energy per nucleon more efficiently than fission of heavy nuclei?

• A. Binding energy per nucleon increases toward iron, so light-nucleus fusion moves toward higher binding energy per nucleon
• B. Binding energy per nucleon decreases toward iron during fusion
• C. Fission of heavy nuclei increases binding energy per nucleon, releasing energy
• D. Fusion of light nuclei requires more mass to be converted into energy than fission of heavy nuclei

Answer: (A)