[单选题]
A 3.00-m long pipe is i4.8i z.gpz dhg5hzs *nn a room where the temperature ixp1b9tbf)chgo.65m rd(( jr p+f mf7 ss $20 \; ^{\circ}C$. 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
