(;
AB[lc][ld][jd][md]
AW[hc][hd][ib][mc][mb][ma][oc]
C[Can Black prevent a connection along the top edge?  (Assume that the positions on the left, right, and center are not relevant.)]
(;
B[ja]
C[This edge play often works, but not here.];
W[jb]
(;
B[kb];W[ka]
C[This throw-in tesuji foils Black's plan.];
B[la];W[lb]
(;
B[kc]
C[Black only has a ko.]
)
    (;
    B[ka]
    C[Connecting doesn't work.];
    W[kc]
    )
)
    (;
    B[la]
    C[Mistake.];
    W[lb];B[kb];W[kc]
    C[Black doesn't even have a ko.]
    )
)
    (;
    B[kb]
    C[Also looks promising, but ...];
    W[ka];B[ja];W[jb];B[la];W[lb];B[kc]
    C[Again, Black only has a ko.]
    )
    (;
    B[ka]
    C[Even worse.];
    W[kb];B[lb];W[la]
    C[Black has nothing.]
    )
    (;
    B[jb]
    C[The only move!];
    W[ja];B[ka];W[kb];B[ia]
    (;
    W[jc]
    C[White seems to have a ko, but ...];
    B[lb]
    LB[la:A][kc:B]
    C[A and B are miai for Black to stop the connection without having to fight a ko.]
    (;
    W[la];B[kc]
    )
        (;
        W[ja];B[la]
        )
    )
        (;
        W[la]
        C[Michal, an alert reader, pointed out that the original solution did not show this important defensive try.];
        B[ic]
        C[Black has this defensive resource.]
        (;
        W[ja];B[hb]
        )
            (;
            W[hb];B[ja]
            LB[jc:A]
            C[After Black connects, White no longer has the atari at A.]
            )
        )
    )
)

