Quadrilaterals ...

Complete the following statement .

Which of the following statements is true?

Consider the following statements and state which one is true and which one is false: 
(1) The bisectors of all the four angles of a parallelogram enclose a rectangle.
(2) The figure formed by joining the midpoints of the adjacent sides of the rectangle is a rhombus. 
(3) The figure formed by joining the midpoints of the adjacents sides of a rhombus is square.

What is the value of $$x$$ in the given figure?

A quadrilateral in which only one pair of opposite sides are parallel is called a ..........

Which of the following statement(s) is/are true?

In a parallelogram, the sum of adjacent angles is:

In the diagram, $$ABD$$ and $$BCD$$ are isosceles triangles triangles, where $$AB=BC=BD$$. The special name that is given to quadrilateral $$ABCD$$ is:

If the bisectors of the angles $$A, B, C$$ and $$D$$ of a quadrilateral meet at $$O$$, then $$\angle AOB$$ is equal to:

In $$\triangle PQR, QR=10, RP=11$$ and $$PQ=12.$$ $$D$$ is the midpoint of $$PR$$. $$DE$$ is drawn parallel to $$PQ$$ meeting $$QR$$ in $$E.$$ $$EF$$ is drawn parallel to $$RP$$ meeting $$PQ$$ in $$F.$$ What is the length of $$DF\: ?$$