Which of the following describes a colorless chemical with a strong odor that is considered hazardous?

The correct choice is formaldehyde, which is a colorless gas known for its strong, pungent odor. It is classified as hazardous due to its potential health risks, including irritation of the eyes, nose, and throat, as well as being a probable human carcinogen. Formaldehyde is commonly used in various industrial applications, including the production of resins and as a preservative in laboratories and mortuaries.

While ammonia is another colorless gas with a strong odor, it is primarily recognized for its application in cleaning products and fertilizers, and its properties and health hazards differ from those of formaldehyde. Chlorine, also a colorless gas with a strong smell, is primarily used for water disinfection and has its own specific health implications. Hydrogen sulfide, although colorless and hazardous, has a characteristic rotten egg smell and is associated with industrial processes and natural sources like swamps.

These nuances highlight why formaldehyde is the most apt description in the context given, emphasizing its distinct characteristics and hazards compared to the other substances.