In which materials is formaldehyde commonly found?

Formaldehyde is commonly found in polymers and resins, primarily because it is used as a key ingredient in the production of various synthetic materials. For instance, it is a component of urea-formaldehyde and phenol-formaldehyde resins, which are widely utilized in adhesives, composite wood products, and insulation materials. These resins are often chosen for their bonding capabilities and durability, making them prevalent in both construction and furniture manufacturing.

In contrast, other materials listed in the choices—such as concrete, steel, glass, tile, and stone—do not inherently contain formaldehyde. Concrete and steel are inorganic materials, while glass, tile, and stone are also not associated with organic compounds like formaldehyde. Wood can contain formaldehyde in certain treated forms and products, but it is primarily the synthetic polymers and resins that are significant sources of this chemical in various applications. Hence, the correct identification of polymers and resin as commonly containing formaldehyde is accurate.