A beam of light moves through a vacuum before it goes into a liquid. The diagram illustrates its route. In the vacuum, the light travels at a speed of $3.0 \times 10^{8}\,\text{m s}^{-1}$. What is the speed of light in the liquid?
- A$1.9 \times 10^{8}\,\text{m s}^{-1}$
- B$2.0 \times 10^{8}\,\text{m s}^{-1}$
- C$4.6 \times 10^{8}\,\text{m s}^{-1}$
- D$4.8 \times 10^{8}\,\text{m s}^{-1}$