A device that restricts body movement is a:

A device that restricts body movement is a physical restraint.

Physical restraints are specifically designed to limit a person's mobility, often used in medical and caregiving settings to ensure safety or prevent injury. These devices help manage patient behavior and movement, particularly in situations where individuals may pose a risk to themselves or others.

This choice directly describes a device intended to restrict body movement. Physical restraints can include various tools such as belts, straps, or other mechanisms that limit motion, ensuring safety in clinical environments.

A lap cover is typically used for warmth or comfort, rather than to restrict movement. While it may cover the legs, it does not serve the purpose of limiting mobility and is not classified as a restraint device.

An over-bed table is a piece of furniture designed to provide a surface for activities such as eating or writing while in bed. It does not restrict body movement; instead, it is meant to enhance convenience and accessibility for individuals who are confined to bed.

A gait belt is used to assist individuals in walking and provide support during mobility; it does not restrict movement but rather facilitates safe movement. It is a tool for caregivers to help prevent falls, not a device designed to confine or limit movement.

In summary, a physical restraint is explicitly defined as a device that restricts body movement, making it the correct answer. Other options, such as a lap cover, over-bed table, and gait belt, serve different purposes related to comfort and assistance rather than confinement. Understanding these distinctions is important in contexts where patient safety and mobility assistance are critical.