Let the side of square be s.
Inradius = $$\frac{s}{2}$$
In $$\triangle OAB$$,
=> OB = $$\sqrt{OA^2 + AB^2}$$
=> OB = $$\sqrt{\frac{a}{2}^2 + \frac{a}{2}^2} = \frac{a}{\sqrt{2}}$$
Their ratio would be :
$$\frac{OA}{OB} = \frac{\frac{a}{2}}{\frac{a}{\sqrt{2}}}$$
So ,the answer would be option a)$$1 : \surd{2}$$.
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