[单选题]
The lowest tone to resonate in an o hfec+q5 u7k1s ,judllf0 5x40tjha,bpen p+.3ifck3 cypk ipe of length L is 400 Hz. What is the frequency of the lowest tone that will resonate in an open k3i 3k.ccy+pfpipe of length 2L?
A. $800 \; Hz$
B. $200 \; Hz$
C. $1600 \; Hz$
D. $100 \; Hz$
