A nucleus with mass number A splits into two daughter nuclei with mass numbers $ A_1 $ and $ A_2 $ ($ A_1 + A_2 = A $). Which condition ensures energy release in the fission process?
Correct: A
Energy is released when the binding energy per nucleon increases, i.e., daughter nuclei are more tightly bound than the parent. This is why fission of heavy nuclei (e.g., U-235) into smaller ones is energetically favorable. The correct answer is A. The student must connect binding energy trends and stability.