A diagonal of a quadrilateral is a line segment that joins two ……………… vertices of the quadrilateral.

We conclude that a diagonal of a quadrilateral is a line segment that joins two opposite vertices of the quadrilateral.

Step-by-step explanation:

From the attached diagram, it is clear that the line segment AC of the parallelogram quadrilateral joins two opposite vertices A and C.

It is also clear that the other line segment BD of the parallelogram quadrilateral joins two opposite vertices B and D.

Therefore, we conclude that a diagonal of a quadrilateral is a line segment that joins two opposite vertices of the quadrilateral.

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