Translation:What helps you to distinguish between those two flashlights?
Sorry if this is a bad question, but I'm curious--what's the particular reason that Team Vietnamese members can't record some of the sentences? Is it a Duolingo rule, a matter of recording quality, a matter of being too strapped for time? Is it considered bad form to use multiple voices?
Since there was no "between" in the clues, I decided it must be a case in which there were five people walking and two of them had slightly different flashlights, or there were a number of flashlights in a drawer, almost the same, but not quite. The question would mean, "How can you tell those two apart from the others?" in which case, "between" wouldn't be either necessary or correct. It could also be a case of responding to someone who'd looked at a bunch of identical ones and said, "These two are mine!"