[单选题]
The expression (MX - MY - Mg ;0c rqzox 28fsk1e/ *,djdtqa) x 9335g-ricd4l*qt.- mklit fy 1y1.5 represents
A. the binding energy of the nucleus X.
B. the binding energy of the nucleus Y.
C. the energy released when nucleus X undergoes alpha decay.
D. the energy released when nucleus Y undergoes alpha decay.