Posted 2012-March-07, 06:43
Sorry, I thought you posed the question as a riddle, not as a genuine question. I'll try to explain why I think the A is right, and better players will hopefully correct me if I'm wrong.
Because dummy has a singleton diamond, and there are seven diamonds out there, even if the K is "onside" (i.e. the Q wins), we won't be able to repeat the winning finesse - we just don't have any more diamonds to lead. So, playing the Q is a losing proposition, pretty much irrespective of where the K is. The fact the 8 was the card that was led is also important: it means my AQJT7 just became solid (i.e. the 7 is a top honor), and it makes it almost impossible for the king to be with the opening leader (assuming they lead high from doubleton, low from honor, etc).
So, I give up on the finesse, and switch to a plan called "ruffing finesse", where I lead my sequence of honors and discard losers from dummy. If the K is "wrong" (for a regular finesse) it's now "right" - if W covers, I can ruff and the rest of my diamonds are good. And if the king was with E, it's no biggie, I'll lose a diamond but I already discarded a loser on that trick, so I didn't really lose anything.
The only problem with running the sequence is if I can lose two diamonds - one to the K and one to a ruff. That's why I proposed starting with three rounds of trumps, so even if trumps are 4-1, once you lose one diamond trick to the K, you can draw the outstanding trump and run diamonds.