Answer:
correct answer is (b) Longitudinal lines remain straight
Explanation:
solution
As we know that Deformation of circular shaft in the torsion is associate with twisting of shaft more than an specify with the yielding limit.
so when any angle of twist is obtain in the torsion and that is beyond the specified safety limit of shaft
than that shaft will be fail.
but it does not regain its original shape and it will cause permanent deformation
so that we can say longitudinal lines which is twist, they will not regain to original back position as straight
but they will remain in curved shape.
so here incorrect statement is b Longitudinal lines remain straight