( 3 - 1 3 )^2\, simplifies\, to:

Answer: Option C

$$\begin{array}{rl}& {\left(\sqrt{3}-\frac{1}{\sqrt{3}}\right)}^2\\ & ={\left(\sqrt{3}\right)}^2+{\left(\frac{1}{\sqrt{3}}\right)}^2-2\times \sqrt{3}\times \frac{1}{\sqrt{3}}\\ & =3+\frac{1}{3}-2\\ & =1+\frac{1}{3}\\ & =\frac{4}{3}\end{array}$$