Fatigue is the failure of a material due to $\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_$; it occurs at stresses $\_\_\_\_\_\_\_\_\_\_\_$ a material's tensile

strength

A dynamic $($often cyclic$)$ stresses; above

B dynamic $($often cyclic$)$ stresses; below

C a constant stress; above

D a constant stress; below