Which statement describes the behavior of steel when heated by fire?

• A. They shorten, pulling walls in.
• B. They lengthen, pushing walls outward.
• C. They bend without changing length.
• D. They remain the same.

Answer: (B)

When steel is heated, it expands in length. In a fire, that expansion can push against connected walls or frames if movement is restrained, causing walls to be forced outward. This outward thrust is a direct result of thermal expansion, which is why the statement describing lengthening and pushing walls outward is the best description of steel’s behavior under fire. The other ideas—shortening, bending without length change, or remaining the same—don’t match how steel responds to heat, since heating causes expansion rather than contraction or unchanged length (though localized bending can occur, the primary effect relevant here is length increase).