Statement-I      The tangents at the ends of the diameter of a circle are perpendicular.

Statement-II       The number of circles that can be drawn through three non-collinear points in a plane is one

$XY$  is the diameter to the circle $AB$  and $CD$  are tangents to the circle at end points $X$  and $Y$ . But $\overline{)AXY}=90°\left(\because OX\perp AX\right)$

$\overline{)CYX}=90°\left(\because OY\perp CY\right)$

$\therefore$ $\overline{)AXY}+\overline{)CYX}=90°+90°=180°$

But these are co – interior angles and their sum is $180°$

$\therefore$ $AB\parallel CD$

II)By concept