Answer
All the odd harmonics of pipe B have a frequency that matches a resonant frequency of pipe A.
Work Step by Step
We can write an expression for the harmonics of pipe B:
$f = \frac{nv}{2(2L)} = 0.25~\frac{nv}{L},$ where $n = 1,2,3,...$
We can write an expression for the harmonics of pipe A:
$f = \frac{nv}{4L} = 0.25~\frac{nv}{L},$ where $n = 1,3,5,...$
We can see that all the odd harmonics of pipe B have a frequency that matches a resonant frequency of pipe A.
