Which pliers are characterized by a movable pivot point to adjust the jaws' size?

The correct choice is tongue-and-groove pliers, which are designed with a movable pivot point that allows for easy adjustment of the size of the jaws. This feature provides versatility when gripping various sizes of materials, making tongue-and-groove pliers particularly useful for plumbing and pipe fitting tasks, where the diameter of pipes and fittings can vary significantly.

The adjustable pivot allows the user to reposition the pivot point, expanding the jaw width to accommodate larger objects while maintaining a secure grip. This design is essential for ensuring that a proper hold is achieved on different shapes and sizes, which is critical in avoiding slippage and ensuring accuracy in work.

Other tools, such as long nose pliers, lineman's pliers, and locking pliers, serve different functions. Long nose pliers excel at reaching into tight spaces and gripping smaller objects but do not have an adjustable pivot. Lineman's pliers are designed primarily for cutting and twisting wires, focusing more on grip strength than size adjustment. Locking pliers, while effective for creating a stable hold through a locking mechanism, also lack the adjustable pivot feature that characterizes tongue-and-groove pliers.