Given the Following Balanced Equation,determine the Rate of Reaction with Respect

Given the following balanced equation,determine the rate of reaction with respect to [SO₃].
2SO₂(g) + O₂(g) ? 2SO₃(g)

A) Rate = - $\frac { 1 } { 2 }$ $\frac { \Delta \left[ \mathrm { SO } _ { 3 } \right] } { \mathrm { D } t }$
B) Rate = + $\frac { 1 } { 2 }$ $\frac { \Delta \left[ \mathrm { SO } _ { 3 } \right] } { \Delta t }$
C) Rate = - $\frac { \Delta \left[ \mathrm { SO } _ { 3 } \right] } { \mathrm { D } t }$
D) Rate = + $\frac { 2 \Delta \left[ \mathrm { SO } _ { 3 } \right] } { \Delta t }$
E) It is not possible to determine the answer without more information.