If someone takes the line of showing one card, take it as in general they have you beat.
Usually people who show one card actually have the best hand, even if the card they are showing is irrelevant.
They show one card to make you think they bluffed, when in fact, it means the opposite in most cases. You will always find as well; it's always on a flush/straight or paired board they show the irrelevant card, as they actually have the nut straight/nut flush or trips on the paired board with the other one card they didn't show. They will also take the showing one card on a like well connected board with over cards but actually have a set..for example; K,A,8,9,2 they will show the "weak" card as a 2, when infact they hold pocket decues so there "plan" is to make u think you folded the better hand or two pair or Ax and they bluffed you with bottom pair but of course they actually have the best had with the set.