ANS:C - yield

Factor of safety is the ratio of the yield stress to the working stress. The factor of safety is a measure used in engineering to indicate the margin of safety in a design. It is calculated as the ratio of the yield stress of the material to the working stress, where the working stress is the stress level that the material is expected to withstand during normal operation without failure. By comparing the working stress to the yield stress, the factor of safety helps ensure that the design can withstand loads beyond normal operating conditions and provides a margin of safety against unexpected overloads or variations in material properties.