A string is taut between a vibration generator and a fixed point. When the vibration generator is oscillating with frequency $f$, a stationary wave is formed on the stretched string with five nodes, as shown. A node is present at the end of the string attached to the vibration generator. The frequency of vibration of the vibration generator is then increased slowly. What is the next frequency that produces a stationary wave on the string?
- A$1.25f$
- B$1.50f$
- C$1.75f$
- D$2.00f$