The toughness of a metal is best defined by which of the following?

Toughness is best defined as the ability of a metal to absorb energy and deform plastically without fracturing. This characteristic is crucial in applications where materials are subjected to sudden impacts or loads that could cause failure. Toughness is typically measured through tests like the Charpy impact test, which evaluates a material's resistance to brittle fracture under high strain rates.

The emphasis on both energy absorption and plastic deformation distinguishes toughness from other mechanical properties. While some materials may be strong and able to withstand high loads, if they are brittle, they may fail suddenly without significant plastic deformation. Hence, toughness combines both strength and ductility, which are essential for structural performance in engineering applications.

In contrast, options that discuss characteristics such as high-temperature resistance, wear and abrasion resistance, or yield strength do not adequately capture the essence of toughness. Those features relate to other aspects of material performance but do not specifically address the capability to absorb energy and deform without breaking.