If two vertices of an equilateral triangle are $(0,0),(3, \sqrt 3)$, then the third vertex is _________

Question

$\begin{array}{1 1}(A) \; (2 \sqrt 3,0)\\(B)\;(0,2 \sqrt 3)\\(C)\;(\sqrt 3, 0) \\(D)\;(0, \sqrt 3) \end{array}$