2012-II-41
Ans: C
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Join $OB$.
$\begin{array}{rcl}
\angle BOQ & = &

Join $OB$.
$\begin{array}{rcl}
\angle BOQ & = &
$\because AB$ is the diameter,
$\the
$\because \ov
Since $AD$ is a radius of the
$\therefore \angle ADB = \angle D

$\begin{array}{rcl}
\angle BAC & = &

Join $CD$. Since $AC$ is a diameter, then $\angle ADC =

Join $AC$.
$\begin{array}{ll}
BC = CD & \text{(

Since $AC$ and $BD$ are diameters of the circle, then t
$\b

Since $ABCD$ is a rhombus, then we have $BC\text{//}A

Join $BD$. Consider $\Delta PBD$, we have
$\begin{ar

In quadrilateral $ABCD$,
$\begin{array}

Since $DE$ is the tangent to the circle at $A
