Final answer:
An (a) over-receipt occurs when the quantity received is greater than what was requisitioned but matches the supplier's shipped quantity.
Step-by-step explanation:
When the quantity received is greater than the quantity requisitioned but equal to the quantity shipped, what we have is an over-receipt. This occurs when a buyer receives more items than were requested on the purchase order, though the number of items matches what the supplier claims to have sent.
This situation may be due to an ordering or shipping discrepancy, but it does not constitute a shortage since the receivers got more than they requisitioned for, nor an excess because it matches the supplier's shipped quantity, and it is not a mismatch since the received and shipped quantities align.