TIME DELAYS AND PHASING

 Correct 

Phasing depends on the delayed sound being out of phase with the original, by 1/2 wavelength, as well as its odd multiples, 1, 3, 5, so those represent the cancelled frequencies.
Frequencies whose wavelength correspond to the delay are in phase with each other, so those frequencies are reinforced, which is a set of even harmonics, 2, 4, 6.