One Reaction That Occurs in an Automobile Catalytic Converter Is $\rightarrow$

One reaction that occurs in an automobile catalytic converter is the conversion of nitrogen monoxide to nitrogen and oxygen. How could the rate of this reaction be expressed correctly in terms of the rate at which the concentration of a reactant or product changes?
2NO(g) $\rightarrow$ N₂(g) + O₂(g)

A) Rate = $\Delta$ [NO]/ $\Delta$ t
B) Rate = - $\Delta$ [NO]/ $\Delta$ t
C) Rate = $\frac { 1 } { 2 }$
$\Delta$ [NO]/ $\Delta$ t
D) Rate = - $\frac { 1 } { 2 }$
$\Delta$ [NO]/ $\Delta$ t
E) Rate = 2 $\Delta$ [NO]/ $\Delta$ t