Stress and strain — practice question

A metal wire of uniform cross-section, with length $L$ and diameter $d$, has spring constant $k$. What is the Young modulus of the metal?

• A$\frac{\pi d^2}{4kL}$
• B$\frac{\pi d^2}{kL}$
• C$\frac{kL}{\pi d^2}$
• D$\frac{4kL}{\pi d^2}$