What Concession Was Made to Southern Delegates to Gain Their

What concession was made to southern delegates to gain their support for the federal government's power to
Regulate trade policies?

A) Northern delegates agreed to never pass tariffs that favored manufacturing interests.
B) A promise by James Madison that southern states could nullify federal laws.
C) Delegates returned to the original idea of entirely proportionate legislation.
D) Northern delegates agreed to drop demands for abolition of the slave trade.