[单选题]
A 3.00-m long pipe is in a room where the te5l3r ji nct)pntjb 4e9 73gz5rmperature i :gdmho6qp 3n(v4z0 l uk3hep1s $20 \; ^{\circ}C$. 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
