Which substances are carcinogens that can cause cancer?

• A. Mercury and Lead
• B. DDTs and PCBs
• C. PCB, pesticides, dioxin, and flame retardants
• D. Chlorine and ultraviolet light

Answer: (C)

Carcinogens are substances that can cause cancer. Some environmental chemicals have strong evidence that they can initiate or promote cancer, either in humans or in animal studies, and they tend to persist or bioaccumulate in the environment.

This option is the best because it groups several well-known or suspected cancer-causing substances: PCBs, various pesticides such as DDT, dioxin, and certain flame retardants. Dioxin is one of the most strongly linked carcinogens, and PCBs and some flame retardants are persistent pollutants that raise cancer risk with long-term exposure. Including pesticides, dioxin, and flame retardants captures a broad set of chemicals with established or suspected links to cancer.

The other choices mix substances that aren’t primarily recognized for cancer risk (for example, heavy metals are highly toxic in ways other than cancer, and chlorine and ultraviolet light don’t together represent as comprehensive or clear a cancer-causation profile).