[单选题]
A 3.00-m long pipe is ogzfz k yveam)zq7 n4us;6 87imt(: 2qin auptb+d (ek nf4-:oo6f room where the temperature is $20 \; ^{\circ}C$. What is the frequency of the second harmonic if the pipe is closed at one end?
A. $57 \; Hz$
B. $114 \; Hz$
C. $29 \; Hz$
D. none of the above
