Analogy — Scissors : Lever :: Toothed wheel : ? Choose the machine element category to which a toothed wheel belongs, just as scissors function as a form of lever.

Introduction / Context:
This analogy tests basic mechanical concepts and machine elements. Scissors operate as a compound lever, demonstrating how a specific tool fits into a broader simple machine category. We must classify a toothed wheel in the same categorical way.

Given Data / Assumptions:

• Scissors are modeled as two levers sharing a fulcrum at the pivot.
• A toothed wheel is a wheel with teeth along its rim used to transmit motion and torque.
• Options include wedge, gear, press, and pulley, plus a catch-all choice.

Concept / Approach:
We preserve the relation “specific device : category of mechanism.” Scissors map to lever. A toothed wheel used for meshing and transmitting motion is, by definition, a gear. While a pulley is also a wheel, it is smooth and works with a rope or belt rather than interlocking teeth. A wedge is a different simple machine. A press is a machine or operation, not the category for a toothed wheel.

Step-by-Step Solution:

Verification / Alternative check:
In mechanical design, gears are toothed wheels that mesh to change speed, torque, or direction of motion. Pulleys have grooves for belts or ropes and lack teeth by default, so they do not satisfy the toothed specification.

Why Other Options Are Wrong:

• Wedge — a distinct simple machine, unrelated to toothed meshing.
• Press — an application machine, not a category for toothed wheels.
• Pulley — a grooved wheel, typically not toothed in the gear sense.
• None of these — incorrect because gear is correct.

Common Pitfalls:
Equating any wheel with pulley or ignoring the critical descriptor “toothed,” which points directly to gear classification.

Final Answer:
Gear