If $\large\frac{\sqrt 3-1}{\sqrt 3+1}=$$a-b\sqrt 3$ then the value of $a$ and $b$ are __

Question

$\begin{array}{1 1}(A) \; a=2,b=1\\(B)\;a=2,b=-1 \\(C)\;a=-2,b=1 \\(D)\;a=b=1 \end{array}$