1. Identify the nucleus

   The isotope is ${}_5^{12}B$.

   So,

   • Atomic number: $Z = 5$
   • Mass number: $A = 12$

   Hence number of neutrons is $N = A - Z = 12 - 5 = 7.$

2. Write the formula for nuclear binding energy

   Nuclear binding energy is the mass defect multiplied by $c^2$: $\text{B.E.} = \Delta m \, c^2.$

   The mass defect is $\Delta m = (\text{sum of masses of constituent nucleons}) - (\text{actual nuclear mass}).$

3. Compute mass of constituent nucleons

   The nucleus contains:

   • $5$ protons of mass $M_p$ each
   • $7$ neutrons of mass $M_n$ each

   Therefore, $\text{sum of free nucleon masses} = 5M_p + 7M_n.$

4. Use given nucleus mass

   Given nuclear mass of the isotope is $M_0$.

   So mass defect is $\Delta m = 5M_p + 7M_n - M_0.$

5. Binding energy

   Therefore, $\text{B.E.} = (5M_p + 7M_n - M_0)c^2.$

6. Match with options

   This matches Option A: $(5M_p + 7M_n - M_0)C^2.$

Note: The option uses both $M_o$ and $M_0$ notation, but it is clearly intended to denote the given isotope mass.