Answer: a
. By issuing tighter emissions rules
Explanation:
The Environmental Protection Agency (EPA) is the federal body that is tasked with protecting the environment as best they can.
One way they can enforce a ban on factory emissions is by issuing tighter emission rules that would make it more difficult for violators to get away with factory omissions. These rules would act as a deterrent to erring companies and individuals and therefore achieve its goal to some degree.
