Fatigue life is expected to increase by

ANS:C - having compressive residual stresses at the surface.

Shock-resisting steels should possess high toughness. Toughness is the ability of a material to absorb energy and deform plastically before fracturing. In applications where shock loads or impact forces are expected, such as in the case of shock-resisting steels, high toughness is crucial to prevent catastrophic failure. Toughness allows the material to withstand sudden and severe loading without fracturing, which is essential for maintaining structural integrity and preventing brittle fracture under impact conditions. While other properties like hardness, tensile strength, and wear resistance are important in various applications, they may not be as critical for withstanding shock or impact loads. In contrast, toughness is specifically related to a material's ability to resist fracture under dynamic loading conditions, making it particularly important for shock-resisting steels.