A train horn produces sound at frequency $f_1$. As the horn continues to sound, the train travels straight towards a person at rest. The train's speed is $0.20v$, where $v$ denotes the speed of sound. The frequency of the sound received by the person is $f_2$. What is the ratio $\frac{f_1}{f_2}$?
- A$\frac{0.80}{1}$
- B$\frac{1}{1.2}$
- C$\frac{1.2}{1}$
- D$\frac{1}{0.80}$