yaya17 : Black to kill
What about the sequence B-D19, W-B19, B-D18, W-A18 ? White is alive, and so is black. Perhaps the problem should be labeled as 'Black to live' ? Thank you for your attention
Ruknight: This tsumego is incorrect? It says the correct sequence is C19, A18, B19. But, if white plays B19 instead of A18 it becomes a ko again like in the incorrect variation of D18 first move
d4rkm4tter: Yes, so C19 first move is incorrect as it results in ko.
Changed problem from "b to live" to "b to kill", there is only one correct sequence now.