Why were state constitutions significant when the U.S. Constitution was written?

A.
By using the state constitutions as models, the delegates to the Constitutional Convention avoided almost all disagreements.

B.
Most of the U.S. Constitution was directly copied from state constitutions.

C.
The people who wrote the state constitutions had learned valuable lessons about writing a constitution.

D.
State constitutions did not guarantee rights, so the authors of the U.S. Constitution included a bill of rights.