The stress $\sigma$ required to break a certain solid is described by $\sigma = k \sqrt{\frac{\gamma E}{d}}$, where $E$ represents the Young modulus, $d$ is the separation between atomic planes, and $k$ is a constant with no units. What are the SI base units of $\gamma$?
- A$\text{kg m s}^{-2}$
- B$\text{kg s}^{-2}$
- C$\text{kg m s}^{-1}$
- D$\text{kg s}^{-1}$