For the rection $SO_2(g)+\large\frac{1}{2}$$O_2(g)\leftrightharpoons SO_3(g)$ if $K_P = K_C (RT)^X$ where the symbols have usual meaning then the value of x is: (assuming ideality)

Question

$\begin{array}{1 1}(A)\;\large\frac{1}{2}\\(B)\;1\\(C)\;-1\\(D)\;-\large\frac{1}{2}\end{array}$