$M_n$ and $M_p$ represet the mass of neutron and proton respectively. An element having mass M has N neutron and Z-protons, then the correct relation will be : -

Question

( A ) $M < \{N.M_n + Z.M_p\}$
( B ) $M = \{N.M_n+Z.M_p\}$
( C ) $M > \{N.M_n + Z.M_p\}$
( D ) $M=N\{M_n + M_p\}$