[单选题]
The expression (MX - MY - hp p:2i8xgv*wv q5/ (oiv ;/fwrct7buMa) x 931-hfrc+nvdt20,/ba g f.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.