Problem diagram.
Black plays.

Did Go World make a mistake on a tsumego problem?

Source:
Go World #117, Winter 2008-2009, p. 51, tsumego problem #8

Solution follows    (or click here to download SGF)

Official solution.
Go World gives Black 1 as the only killing move. After Black 3, White is clearly dead. But see the following diagrams.

Alternate solution?
Go World says that Black 1 is a mistake, but this play also seems to kill White. Go World only gives Black 3 as a follow up. And White 4 will indeed make a 2nd eye after capuring the 3 Black stones.
But see the next diagram for a better Black attack.

Black refutation.
But Black has the atari at 3 to destroy White's 2nd eye! White dies. Is Go World's analysis wrong?

White variation.
Note that White could try the counter-attack at 2. In the sequence that follows, White can capture a couple stones on the right edge, but White has only 1 eye, and cannot escape to the center.

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