If the initial tube had a resonant frequency of 168Hz and the tube doubled in length , what is the new resonant , and is it inverse or direct

i think it’s a. this is because if they measured the mass of something with a mass of 150g, then their final answer would have to be approximately 150g. though all of their answers are almost 150, rosa and tran have the closest answers (or the exact answer) to the accurate one.

where’s the list ? the question is incomplete