A glass tube is sealed at one end and fitted with a loudspeaker at the other, as shown. When the sound has frequency $f_0$, a stationary wave is produced with a node at the sealed end of the tube. No other nodes are present. The sound frequency is then gradually increased. What frequency of the sound gives the next stationary wave?
- A$1.25 f_0$
- B$1.50 f_0$
- C$2.00 f_0$
- D$3.00 f_0$