Question

would give congress the ability to control, or even end, the slave trade. southern delegates threatened to leave the union if congress had the power to control the slave trade. so northern delegates agreed that, for 20 years, congress would not pass laws banning slavery. this agreement is known as the slave - trade compromise.
what did the slave - trade compromise do?
it prevented northern merchants from getting the economic benefits promised by the commerce clause.
it allowed congress to regulate trade but prevented congress from banning slavery for 20 years.
it made it possible for congress to provide revenue for foreign slave - trade markets.
it forced southern states to immediately end the slave trade because it was no longer profitable.

Explanation:

The text states that northern delegates agreed Congress would not pass laws banning slavery for 20 years as part of the Slave - Trade Compromise while still allowing Congress to regulate trade.

Answer:

It allowed Congress to regulate trade but prevented Congress from banning slavery for 20 years.