live play, no showdown, show one or both cards?

[KKrAAAzy88s]

in live play, say you win the pot uncontested, can you show just one of your hole cards and not the other? or if you show, do you have to show both?

example i guess would be you have pocket 4s and you hit your set. there was a raise and you reraise and take down the pot. can you show just one of your hole fours and show them bottom/middle pair. no real reason to this question, just curiousity.