Regulating interstate commerce is a duty of which level of government?

Federal Government regulates the interstate commerce. It refers to the procurement or sale of any merchandise within the states or in between the states is regulated by the states government.  

Federal Government is declared to regulate the interstates commerce and trade as specified in the constitution. Interstate trade was controlled by Interstate commerce commission which organized interstate trucking, Shipments and transportation of goods through freeways.  

Later, this control is transferred to the Federal Department called Transportation Department after the Sherman Act.

answer; ///i do believe that the correct answer is (d); ///athens had a small population;

i think it was because of how protected egyptian civilization was was which allowed them to evolve without much outside influence.