Solution by lavalyn:
eliminates the eye at the edge - a and b are miai for the white group escape to safety.
here fails after
- he will take the marked point without difficulty, making the second eye.
While the peep of must be answered, the kill still requires
.
Curious to know what would happen if was played. Looks right in my head.
unkx80: is correct too as it makes miai of a and b but I don't think this will be encouraged because it might be making extra investment for the same returns.
victim: This will give B an extra ko threat at a. Always play in the way giving the opponent as few threats as possible (everything else being equal) and as small threats as possible.