What is the sum of the coefficients for the equation when balanced using the smallest possible whole numbers?

__ ${{\text{N}}_2}{{\text{H}}_4}({\text{g)}} +$ __ ${{\text{O}}_2}{\text{(g)}} \to$ __ ${\text{N}}{{\text{O}}_2}{\text{(g)}} +$ __ ${{\text{H}}_2}{\text{O(g)}}$

A.     5

B.     6

C.     7

D.     8

D