Rib refers to which of the following?

• A. A line used to show the alternate positions of an object.
• B. A US federal agency with a mission to protect human health and the environment.
• C. A relatively thin flat member acting as a brace support.
• D. The study of workplace equipment design or ergonomics.

Answer: (C)

Rib is a relatively thin flat member that acts as a brace or stiffener to strengthen a panel or shell. When you have a thin surface, it can easily bend or buckle under load. Adding ribs along or inside the surface increases stiffness, distributes loads more evenly, and reduces deflection without adding a lot of weight. You’ll see ribs used in many designs, like aircraft skins, computer enclosures, and automotive panels, where the goal is to keep the surface from bending while keeping the overall weight down. This matches the idea of a structural reinforcing element, rather than a line showing alternate positions, a government agency, or a study area.