need help answering the question below please explain your a

need help answering the question below.
please explain your answer.
thanks

The fatigue strength modification for surface finish is related to Choose all that are correct a. exposure to a corrosive environment b. the average roughness of the surface c. yield strength in tension d. the method of fabrication/finishing processes used e. surface treatments

Solution

a. exposure to a corrosive environment

Reason: Surfaces which are corroded perform very poor in fatigue

b. the average roughness of the surface

Reason:-If we increase surface roughness it leads to cracks on surface, and leads to step-wise S-N curves.

d. the method of fabrication/finishing processes used

Reason:- if the sample is highly polished is will eliminate irregularities that lead to crack formation.