What tool is primarily used to loosen and tighten lug nuts?

The correct answer is a wrench, specifically a lug wrench or a socket wrench, which is designed explicitly for the purpose of loosening and tightening lug nuts on a vehicle's wheels. Lug nuts are torqued to a specific tightness and require a tool that can provide the necessary leverage and fit.

A wrench enables the user to apply significant torque to the nut, making it easier to either remove a wheel or securely fasten it back onto the vehicle. The design of a lug wrench often includes a cross or L-shape to facilitate this process, providing the user with a firm grip and leverage.

Other tools mentioned, such as a jack, are used to lift the vehicle in order to access the wheels but do not have any function for actually tightening or loosening lug nuts. A screwdriver is typically designed for turning screws and lacks the appropriate dimensions and grip needed for lug nuts. Pliers can grip objects but do not provide the same leverage or fit required for lug nut engagement. Therefore, the wrench stands out as the appropriate tool for this specific task.