[单选题]
An organ pipe open at both ends has a lec93b :- lijxqqa0zd0 xx8q4 h0wlw*skngth of 0.80 m. If th qdw7tw07wbbtc k.;i4:bwj a1 e velocity of sound in air is 340 m/s, what is the frequency of the sectqajtb7w 4 :bww 1bw7.;ic0d kond harmonic?
A. $213 \; Hz$
B. $425 \; Hz$
C. $638 \; Hz$
D. $850 \; Hz$
