Answer:
Concentration factor will be 1.2
So option (C) will be correct answer
Step-by-step explanation:
We have given outer diameter D = 1.25 in
And inner diameter d = 1 in and fillet ratio r = 0.2 in
So
ratio will be

And
ratio will be

Now from the graph in shaft vs torsion the value of concentration factor will be 1.2
So concentration factor will be 1.2
So option (C) will be correct answer.