Choose the odd one out: ADG, BEH, CFI, DHL.

In ADG the places are 1, 4, 7, in BEH they are 2, 5, 8 and in CFI they are 3, 6, 9, so each group steps up by 3 and then by 3 again. DHL runs 4, 8, 12, stepping up by 4 twice. All four groups look alike because every one of them is evenly spaced; only the size of the gap separates the odd group from the rest.