Skipping all of the discussion about a different hand: Partner probably has a decent hand (10-11+)without a long major. Declarer could easily be void in either major. Leading a diamond does nothing for the defense, and could easily finesse partner holding Kx(dummy void). Leading either Ace could set up overtricks when the board shows up with the right cards. I can quickly design hands with eight diamonds, a major suit void opposite a key five, running 13 tricks by ruffing the major suit ace at trick one. Declarer's contract appears to be sound. That leaves the club suit: Its more likely declarer has clubs than either hearts or spades. Leading the King could be easily be self-finesse, even given its more likely than not declarer doesn't have the Ace. On the eight of clubs I'm hoping to find partner with the ace, a club return or major suit finesse at trick two, and hopefully results in set before yielding control to declarer. In the alternative, if dummy has the ace, my King is probably dead anyway, but declarer is forced to make a key decision at trick one, when he has less information. If partner doesn't have the ace, the doubleton is unlikely to be recognized in time, and I'll probably still get the King of clubs in any scenario where I would have gotten it with protection. More simply, baring the king of clubs by leading the eight most likely leaves me no worse off, and could result in a quick set. Any other card could result in overtricks. I lead the eight of clubs.