Which substances are classified as chemical poisons?

The classification of substances as chemical poisons typically involves their ability to cause harm to biological systems, often leading to toxic effects even at low doses. The correct answer includes lead, arsenic, and cyanide, all of which are well-documented to be highly toxic and can result in acute or chronic health issues upon exposure.

Lead is a heavy metal that can cause a range of health problems, particularly neurological effects, when accumulated in the body. Arsenic is a known carcinogen and can cause severe poisoning, with symptoms that can result from both short-term and long-term exposure. Cyanide, a rapidly acting poison, interferes with the body’s ability to use oxygen, leading to potentially fatal outcomes.

The other options include substances that have varying degrees of toxicity and are not universally classified as chemical poisons in the same manner. For instance, alcohol, while intoxicating and potentially harmful in excess, is not classified as a chemical poison like the others listed in the correct answer. Similarly, while formaldehyde and mercury are indeed toxic, carbon dioxide is a naturally occurring gas that is generally safe in low concentrations and is commonly encountered in everyday life.