0 short form of who had: --
She wondered who'd sent her the mysterious email.
Well, who'd have thought Joey was going to become so successful?
1 contraction of who would or who had: --
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
Vi kan slutföra det steg för steg hur lång vägen än är och den kan inte slutföras hur kort vägen än är om du inte ens markerar ditt fotavtryck.