The same sequence works if white plays at
.
unkx80: at a...
Fwiffo: Ah, that kills. So the correct answer is the final diagram where black takes four stones and white lives?
Any other response lets black peel off those four stones, and the reduction costs more points than the seki... Before , there were 12 points of territory plus one capture. After, there is just four points plus the prisoner, and black has garnered four points of territory plus four prisoners; a net loss of 16 points. Under Japanese counting, white can get two points in the seki by capturing the black stones in her eyes on top of the two previous captures; a net loss of only 9 points.
Anyhow, that's what I get. Wrong, right? -- Fwiffo