A mathematics teacher discusses the concept of open and closed curves in class. To test the students' understanding, she gives an example involving four distinct points. If the curve drawn through these points is a simple open curve (like a line segment), which of the following must be true about the nature of these four points?

If B is the center of a circle and lines AD and CD are tangent segments drawn from an external point D, then which of the following classifications apply to quadrilateral ABCD? (a) Kite (b) Cyclic quadrilateral (c) Rhombus (d) Trapezium

In a parallelogram PQRS, rays PA and SA are the angle bisectors of ∠QPS and ∠RSP respectively. Find the measure of ∠PAS.