[单选题]
An organ pipe open at both ends hav f)du5mx30hrehyu0 1 s a length of 0.80 m. If th :a.shlr 38ifhe velocity of sound in afs.:hlr 8 ih3air is 340 m/s, what is the frequency of the second harmonic?
A. $213 \; Hz$
B. $425 \; Hz$
C. $638 \; Hz$
D. $850 \; Hz$
