The cross sections of two hollow bars made of the same material are concentric circle as shown in the figure. It is given that r3 > r1 and r4 > r2, and that the areas of the cross-sections are the same. J1 and J2 are the torsional rigidities of the bars on the left and right, respectively. The ratio J2/J1 is

• A. > 1
• B. < 0.5
• C. 1
• D. between 0.5 and 1