Given,
In a parallelogram ABCD
Since diagonal of parallelogram bisects each other
OA = OC and OB = OD
Since P&Q are the point of trisection of BD
BP = PQ = QD
Now,
OB = OD and BP = QD
OB-BP = OD-QD
OP = OQ
Diagonals of quadrilateral bisect each other
Hence,
APCQ is a parallelogram.