Under this policy, when a territory's population reached 60,000 they could petition congress for statehood.

This was the Northwest Order of 1787 - Created and unified the Northwest Territory, the first organized territory of the United States, encompassing the lands on the north side of the Ohio River, and east of the Mississippi River. This ordinance would create the precedent of dividing and organizing the lands to the West, and when the population of a territory reached 60,000 inhabitants or more, they could ask that this territory become a state. Another important fact of this Ordinance was that slavery was prohibited in these new states that would be created. The Ohio River was established as the boundary between the zone of forbidden slavery and legal slavery, which prepared everything for the emergence of free states and slave states.

Uh

The answer b is correct this all occurred during the red scare