Which of the following statements best describes the proceduresunder the Clean Air Act? A. The stat

Which of the following statements best describes the proceduresunder the Clean Air Act? 

A. The state governments set and enforce the standards.

B. Both the federal and state governments set standards and eachenforces its own standards.

C. The federal government sets and enforces the standards

D. The federal government sets the standard; the state governmentenforces the standards; if the state governments do not adequatelyenforce the standards, the federal government may enforce them.