In the Credit Terms of 2/10,n/30,what Does the 2/10 Mean

In the credit terms of 2/10,n/30,what does the 2/10 mean?

A) The invoice must be paid in 2 days or a 10% late charge will be assessed.
B) The invoice was printed 2 days after the sale and is due in 10 days.
C) The goods shipped took 2 days to arrive and the charge was $10.00.
D) The purchaser may take a 2% discount if the invoice is paid in 10 days.