What is a trade discount received?

A、Anallowancegivenbyasuppliertoreducethevalueofaninvoicereceived.;
B、Areductionininvoicepriceasaresultof(eg)buyinginquantity.;
C、Asupplierresponsewhenadebitnoteisreceived.;
D、Adiscountforpromptpayment.