2h is a loosely bound isotope of hydrogen, called deuterium or heavy hydrogen. it is stable but relatively rare — it form only 0.015% of natural hydrogen. note that deuterium has z = n, which should tend to make it more tightly bound, but both are odd numbers.

2H consists of one proton and one neutron. The atomic mass of a proton is 1.00782u. The atomic mass of a neutron is equal to 1.00866u
Total mass=2.016u and mass of deuterium is equal to 2.01u
Mass difference= 0.002388u
BE = 0.002388×(3×108)²
=3.56912×10-13J
=2.230 Mev
=1.1153 Mev/nucleon

1) according to the law of conservation of mass ,in all chemical reactions total mass is unchanged

The answer is a. mars