Question

what are the two types of standards established for critical pollutants under the clean air act? urban and rural standards city and county standards formal and casual standards primary and secondary standards

Explanation:

Under the Clean Air Act, the two types of standards for critical pollutants are primary (to protect public health) and secondary (to protect public welfare like visibility, ecosystems). The other options (urban - rural, city - county, formal - casual) don't relate to Clean Air Act pollutant standards.

Answer:

D. primary and secondary standards (assuming the last option is D; if the options were labeled as A: urban and rural standards, B: city and county standards, C: formal and casual standards, D: primary and secondary standards, then the correct answer is D. primary and secondary standards)