Final answer:
The bumps on a gear are called teeth. They are crucial for the gear function, allowing them to mesh with other gears or racks to convey motion and force. The correct option is C.
Step-by-step explanation:
The bumps on a gear are called teeth. These teeth are critical components of a gear, as they interlock with the teeth of another gear or rack to transmit torque and rotational motion. The number of teeth on a gear, along with their size and shape, determines how the gear interacts with others, influencing factors such as speed, force, and the direction of movement. Hence, C is the correct option.