Answer:
National standards, grants-in-aids, overriding power
Explanation:
The federal government can standardize policies between states by setting national standards which the states are bound to comply with.
The federal government also ensures standardization by overriding states laws and policies that are inconsistent with federal policies.
The federal governments can also use grants-in-aids to compensate states whose policies are similar to those supported by the federal government thus causing other states to adopt those policies.
They are called the "control group"
I can answer the cotton gin one it was a invention used to pick the seeds of cotton made it faster for cotton picking in the south
