Which among the following are the factors, affecting factor of safety?

Which among the following are the factors, affecting factor of safety?
(I) Dependability of material
(II) Load conditions such as static, varying or shock loads
(III) Selected values of strength characteristics
(IV) Degree of accuracy force analysis of members.

a. (II) and (III)
b. (II), (III) and (IV)
c. (I), (II) and (III)
d. All the four (I), (II), (III) and (IV)

Correct Answer : d. All the four (I), (II), (III) and (IV)

Explanation :

The factor of safety is ratio is critical stress to allowable stress and these two stresses are depend upon all the factors mentioned above. Thus all above factors are affecting factor of safety.