[单选题]
A 3.00-m long pipe is in ag el c8wsh)3g2 room where the tempenu53 bvkr 5q-erature 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
