This is a picture of the Duke Steam power plant in Semora, NC $($near Roxboro$).$ It began operation in $1966,$ with two expansions in $1973$ and $1980.($note these expansion dates in relation to the initial $1970$ passage of the Clean Air Act and its major amendment in $1977)$

When EPA issued National Ambient Air Quality Standards $($NAAQS$)$ regulations under the Clean Air Act of $1970,$ the Semora plant contributed two criteria pollutants, Nitrogen Dioxide $($NO$2)$ and Sulfur Dioxide $($SO$2),$ to the Air Quality Control Region $($Northern Piedmont$)$ for that location. When the Clean Air Act was enacted in $1970,$ and North Carolina thereafter received approval for its State Implementation Plan. Assuming Duke had made made no modifications to the plant that increased its emissions before $1973,$ what statement below best describes the level of authority the EPA and North Carolina had over Duke Power in the few years after the passage of the Clean Air Act to force it to upgrade its NO$2$ and SO$2$ emissions control technology?

Question $6$Select one:

a$.$

EPA and North Carolina had the authority to force Duke to retrofit the existing facility with the Best System of Emissions Reduction for CO$2,$ regardless of cost to Duke

b$.$

EPA and North Carolina had the authority to force Duke to submit to a New Source Review $($NSR$)$ of the existing facility and implement the Best System of Emissions Reduction for CO$2$ to receive a permit to continue operation

c$.$

During this period, EPA and North Carolina had limited if any authority to "technology force" Duke to adopt new systems, because the Clean Air Act in $1970$ did not require New Source Performance Standards $($NSPS$)$ for existing direct sources of criteria pollutants regulated under NAAQS