A Major Reason the Federal Government Began Expanding in Size

A major reason the federal government began expanding in size and authority after the Civil War is that

A) southern states had to be supervised to treat the recently freed slaves fairly.
B) U.S. military power was expanding overseas.
C) the nation was expanding into the frontier territories.
D) the rapid pace of industrialization created a national economy that state governments could not manage.
E) reconstruction efforts demanded the tactics of a dictatorial regime.