[单选题]
The expression (MX - k dn11i5c8 d2n7h vjaqMY c*eeqhs n z(9/- Ma) x 931.5 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.