Answer:
Correct answer is b. It set up a way for all new states to be admitted to the United States.
Explanation:
Option B is correct as this document was adopted in 1787 and according to it, it was established under which terms new countries will bee admitted in the Union.
Option A is not correct as it was established in 1818 along the 49 parallel.
Option C is also not correct as the postal service was established in 1792, although we can trace back its root to the First Continental Congress.
D is not correct as it affected all new admitted countries.