What best describes the I-beam cross-section?

• A. The web forms the curved exterior
• B. The web is a diagonal brace
• C. Flanges (top and bottom) connected in middle by the web
• D. The web is the vertical element at the cross-section

Answer: (C)

An I-beam cross-section is two horizontal flanges, one at the top and one at the bottom, connected by a vertical web. That description—flanges (top and bottom) joined in the middle by the web—best captures the shape. The web is the vertical piece, and its role is to keep the flanges together and carry shear between them, while the flanges provide most of the bending stiffness by being far from the neutral axis. The other options describe shapes or roles that don’t fit this geometry (curved exterior, a diagonal brace), so they don’t match how an I-beam is actually laid out.