Which of the following is a feature of a hammer?

A hammer is specifically designed to drive nails and fasteners into various materials, and a key feature that enables this functionality is the face of the hammer. The face is the flat part at the head of the hammer that makes contact with the nail or fastener. This design allows the force applied when swinging the hammer to be effectively transferred to the nail, ensuring it drives in straight and securely.

The other options describe features of tools that serve different purposes. Adjustable jaws are typically found in wrenches or pliers, allowing for the gripping of various sizes of nuts or bolts. A staple feeding mechanism is characteristic of staplers, which are used to fasten sheets of paper together—not for driving nails. A cutting edge is associated with tools like saws and knives, which are designed for cutting rather than hammering. Thus, recognizing that the primary function of a hammer is to strike and drive fasteners firmly supports the choice of the hammer's face as its defining feature.