[Retros] A different kind of retro problem...

[Noam Elkies]

Seen on chessbase.com <www.chessbase.com/newsdetail.asp?newsid=6110>:
a position from actual play with the questions:

  The black knight is attacked, but onto which square it should go now
  is only one question (A).  The other interesting issue is:

  (B) what was actually White's last (and best!) move, as a reaction to

  (C) which black move? 

  What do you think, Watson?

Note that the pawn structure and wNd4 indicate that this is a
Sicilian middlegame, which argues against the obvious retraction
0 e3-e4.

NDE