Which of the following is NOT a type of gear?

• A. Spur gear
• B. Helical gears
• C. Bevel gears
• D. Chain

Answer: (D)

Gears rely on rigid toothed components whose teeth mesh directly to transfer rotation and torque between shafts. Spur gears have straight teeth and mesh with another spur gear; helical gears use angled teeth for smoother, quieter operation; bevel gears are shaped to transmit motion between intersecting shafts. A chain is not a gear; it’s part of a chain drive where a flexible loop of linked metal engages sprocket teeth. The motion is transmitted via the chain wrapping around sprockets, not by direct meshing of gear teeth. Therefore, the item that is not a gear is the chain.