[单选题]
An organ pipe open at both wqw.gb4rqp*:gb t+;;jy tq quo(6ax,ends has a lengthy5ow:s5qhc9sax/b o3 of 0.80 m. If the velocity of sound in air ih wyo/55q xc9:ba3s sos 340 m/s, what is the frequency of the second harmonic?
A. $213 \; Hz$
B. $425 \; Hz$
C. $638 \; Hz$
D. $850 \; Hz$
