Final answer:
The delegates agreed on how slaves would be counted in the census, known as the Three-Fifths Compromise.
Step-by-step explanation:
The compromise over slavery that the delegates agreed upon during the Constitutional Convention is option
A. Delegates agreed on how slaves would be counted in the census.
This compromise is known as the Three-Fifths Compromise. It stated that each slave would be counted as three-fifths of a person when determining a state's population count for representation and taxation purposes. This compromise was a controversial and heavily debated decision, but it was ultimately reached to balance the interests of both the northern and southern states.