By the Early 1980s,which Statement Was TRUE

By the early 1980s,which statement was TRUE?

A) Total emissions were higher than they were before the Clean Air Act of 1970.
B) Total emissions were lower than they were before the Clean Air Act of 1970.
C) Most emissions were due to the construction of new (post-1970) coal-burning plants.
D) The requirements of the Clean Air Act of 1970 had proven too burdensome.