A tour guide is asked to distinguish an Earthman hiding within a party of people from space settlements.
This story shares the background of Good Taste, which is an infinitely better story and should be read instead. It also shares the basic plot of "I'm in Marsport Without Hilda” which is an infinitely better story and should be read instead. It’s one of a slew of stories commissioned by a non-sf outlet (in this case Seventeen) which may have been fine for a non-sf audience, but is rather on the unpleasant side for an Asimov fan.