(;
AB[fb][ac][bc][gc][hc][ic][cd][dd][ed][fd][be]
AW[ab][bb][eb][ec][cc][dc][fc]
C[Black plays.]
(;
B[ea]
C[Fails.]
(;
W[da];B[cb];W[fa];B[ba]
C[White loses the 2 stones, but ...];
W[gb]
C[... White lives.]
)
    (;
    W[cb]
    C[But defending here is a mistake.];
    B[da];W[gb];B[fa];W[ca];B[hb]
    C[Black can capture the cutting stone to kill White.]
    )
)
    (;
    B[ca]
    C[Fails.];
    W[cb]
    C[For example ...];
    B[ea];W[gb];B[ga];W[da]
    C[... at worst White lives with double ko.]
    )
    (;
    B[da]
    C[Correct.]
    (;
    W[ca];B[ea];W[gb];B[cb];W[fa];B[ba]
    )
        (;
        W[ea];B[cb];W[gb];B[ba]
        )
        (;
        W[gb];B[cb];W[fa]
        (;
        B[ea]
        )
            (;
            B[ba]
            C[Fails.];
            W[db];B[aa]
            C[If Black avoids the ko, ...];
            W[hb]
            C[... White lives.]
            )
        )
        (;
        W[cb];B[ea];W[gb];B[fa]
        C[Black has enough liberties to capture the cutting stone.]
        )
    )
)

