For the reaction, ltBrgt `2NO_(2)(g)rarr2NO(g)+O_(2)(g)` at a certain temperature, the initial rate of decomposition of `NO_(2)` is `0.0036` mol `L^(-1)s^(-1)`. What is the initial rate of formation of `O_(2)(g)` in mol.`L^(-1).s^(-1)`?
A. `0.0018`
B. `0.0036`
C. `0.0054`
D. `0.0072`
