question_answer

Given \[f(x)\,=log\,\frac{1+x}{1-x}\] and \[g\,(x)\,=\frac{3x+{{x}^{3}}\,}{1+3{{x}^{2}}}\], then fog(x) equals

A)  \[-f(x)\,\]             

B)         \[3f(x)\,\]        

C)  \[{{[f(x)]}^{3}}\]           

D)  \[{{[f(x)]}^{2}}\]