The length of the complete circle is called its ............

The line segment joining any two points on a circle is called a ........ of the circle.

$AB$ and $CD$ are two parallel chords of a circle with centre $P$. $l$ is the perpendicular bisector of chord $AB$. Prove that $l$ bisects chord $CD$.

$AB$ is a chord of a circle with centre $P$. Point $C$ is a point other than $A$ and $B$ on the major arc $AB$. If $\angle ACB = 50^{\circ}$,then find $\angle APB$. (in $^{\circ}$)

Write True or False and justify your answer.
The angles subtended by a chord at any two points of a circle are equal.

If arcs $AXB$ and $CYD$ of a circle are congruent,find the ratio of $AB$ and $CD.$