What can cause an open item on the goods receipt/invoice receipt  (GR/IR) account?
A.  Difference between purchase order price and invoice price for a 
purchase order item 
B.  Difference between quantity delivered and quantity invoiced 
for a purchase order item 
C.  Difference between material valuation price and invoice price 
for a purchase order item 
D.  Difference between quantity ordered and quantity invoiced 
for a purchase order item