The Clean Air Act that was passed in 1970 has helped to ______ sulfur compounds in the air.

The Clean Air Act that was passed in 1970 has helped to ______ sulfur compounds in the air.

• A. Increase
• B. Stabilize
• C. Remove
• D. Decrease

Answer: (D)

The main idea is that strong air-pollution rules reduce harmful emissions. The Clean Air Act of 1970 established nationwide standards and required pollution controls on major sources, especially power plants burning coal and oil that release sulfur dioxide and other sulfur compounds. Through emission limits, permitting, and later updates, facilities added pollution-control technologies and switched to cleaner fuels, leading to lower sulfur emissions. So sulfur compounds in the air have decreased as a result. It’s not about removing every trace of sulfur, but about reducing emissions to meet air-quality standards.

The main idea is that strong air-pollution rules reduce harmful emissions. The Clean Air Act of 1970 established nationwide standards and required pollution controls on major sources, especially power plants burning coal and oil that release sulfur dioxide and other sulfur compounds. Through emission limits, permitting, and later updates, facilities added pollution-control technologies and switched to cleaner fuels, leading to lower sulfur emissions. So sulfur compounds in the air have decreased as a result. It’s not about removing every trace of sulfur, but about reducing emissions to meet air-quality standards.