(;CA[gb2312]AP[MultiGo:4.4.4]SZ[19]AB[rq][qp][pp][np][oq][or][op][sq]AW[rp][ro][qn][ql][oo][no][mo][mp][nq][nr][lq][qq][pr]C[Black to play]
(;B[qr]C[Black here to captue one stone seems normal, but the group dies.];W[os]
(;B[pq]
;W[ps]C[There is only one eye in the corner.])
(;B[ps]C[This is a better move than capturing the one stone, but the result is a ko.];W[qs];B[pq];W[rs]
;B[ps]C[It's a simple direct ko, but Black can do better than this.]))
(;B[pq]C[This is the correct move.];W[os];B[ps];W[qs];B[rs];W[rr];B[sr];W[ss]
;B[qr]C[It is a double ko; this is the best result Black can get]))
