[单选题]
A 3.00-m long pipe is in a room where the temp8fy 3t24hspxs+a b .vxermgzyf6 ffl /v8h/ ui7:as*sn)ature 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