Two steel rods of identical length and material properties are subjected to equal axial loads. The first rod is solid with diameter d and the second is a hollow one with external diameter D and internal diameter 50% of D. If the two rods experience equal extensions, the ratio of \(\frac{d}{D}\) is

• A. \(\frac{3}{4}\)
• B. \(\frac{\sqrt{3}}{2}\)
• C. \(\frac{1}{2}\)
• D. \(\frac{1}{4}\)