Let a and b be positive real numbers. Suppose PQ = ai + bj and PS = ai - bj are adjacent sides of a parallelogram PQRS. If the area of the parallelogram PQRS is 8, then which of the following statements is/are TRUE?

A) a + b = 4
B) a - b = 2
C) The length of the diagonal PR of the parallelogram PQRS is 4
D) The vector i + j is an angle bisector of the vectors PQ and PS