In the late 1700s, the passage of the northwest ordinance allowed for the
a. organization of territories and the admission of states.
b. expansion of the united states to twice its size.
c. exploration and establishment of the oregon trail.
d. protection against attacks by american indian tribes.

The passage of the Northwest Ordinance refers to the first Act of 1787 where the Confederation Congress of the United States officially organized the Northwestern territories of Ohio and started its expansion to Western territories by creating new States instead of expanding the previous ones.  The organization of the Northwestern territories of Ohio also served as a way to separate the states who supported slavery and the ones who didn't. Thus the right answer is the option a, organization of territories and the admission of states.