(;
AB[ql][rm][pn][po][qn][sn][op][oq][lq][mq][nq][pr]
AW[rn][ro][rp][qo][pp][pq][qq]
C[Black plays.];
B[rr]
C[The obvious vital point.];
W[qr]
C[Also the only move.  Can you spot Black's correct response now?]
(;
B[rq]
C[Premature.];
W[rs]
C[White lives.];
B[sr]
C[For example ...];
W[sp]
)
    (;
    B[qs]
    C[A mistake.];
    W[rs]
    C[White has this defensive resource.];
    B[ss];W[rq];B[sq];W[or]
    C[Black does not have an outright kill.]
    )
    (;
    B[rs]
    C[Correct.  Now White doesn't even have a ko.];
    W[or]
    C[For example ...];
    B[ps]
    (;
    W[qs];B[rq];W[os];B[sp]
    C[White doesn't have room to make a 2nd eye.]
    )
        (;
        W[rq]
        C[No better.];
        B[qs]
        C[White has nothing.]
        )
    )
)

