If $$f: R \rightarrow R$$ and $$g : R \rightarrow R$$ are defined by $$f(x) = 2^x$$ and $$g(x) = x^2$$ for each $$x \epsilon R$$, then
$$\left\{x \epsilon R : (fog)(x) = (gof)(x)\right\} =$$

A

$$R$$

B

$$\phi$$

C

{0, 2}

D

{0}