The luminosity $L$ of a star is defined by $L = 4\pi r^2 \sigma T^4$, where $r$ represents the star's radius, $T$ denotes the star's temperature, and $\sigma$ is a constant with units $\text{W m}^{-2}\,\text{K}^{-4}$. What are the SI base units of $L$?
- A$\text{kg m}^2\,\text{s}^{-1}$
- B$\text{kg m}^2\,\text{s}^{-2}$
- C$\text{kg m}^2\,\text{s}^{-3}$
- D$\text{kg m}^2\,\text{s}^{-4}$