The point of intersection of the line segments $AB$ and $BC$ is  .

The common arm of $\angle 1$ and $\angle 2$ is _____.

_____ is the diagonal of quadrilateral $ABCD$.

In the adjoining figure, $O$ is the centre of the two circles, identify the radii of the inner circle?

In the adjoining figure, $O$ is the centre of the two circles, then the two circles are called _____ circles.

Only one ray can be drawn with a given initial point.

Two planes intersect in a line.

The interior of a triangle, and the triangle itself make the triangular region.

In a quadrilateral $PQRS$, $\angle P$ and $\angle R$ are a pair of adjacent angles.