Problem 3916 was originally like this but was changed after doubts about the A and B exchange. To the rescue!
(;AW[be]AW[ae]AW[cd]AW[dd]AW[ed]AW[ag]AW[bg]AB[bf]AB[ce]AB[de]AB[ee]AB[cg]AB[dg]AB[bh]AB[ai]AB[ah]AB[ci]AB[cj]AB[bk]AB[bl]AB[am]AB[an]AB[ao]AB[bo]AB[bp]AW[bq]AW[cq]AW[cp]AW[co]AW[cn]AW[bn]AW[bm]AW[cm]AW[cl]AW[ck]AW[dj]AW[di]AW[dh]AW[ch]AW[bj]LB[ah:A]LB[bj:B]C[Black has played A; but White's answer at B aims at capturing the triangled stones...]TR[am]TR[an]TR[ao]TR[bo]TR[bp]AP[goproblems]
(;B[aj]
(;W[aq]C[CHOICE]
(;B[al]
(;W[bi];B[af]C[RIGHT])
(;W[ap]
(;B[bi]C[RIGHT])
(;B[af];W[ak])
(;B[ak];W[bi])
(;B[bd];W[ak])
(;B[cf];W[ak]))
(;W[af]C[CHOICE]
(;B[bd];W[ap]
(;B[bi]C[RIGHT])
(;B[ad];W[ak])
(;B[ak];W[bi]))
(;B[bi];W[cf]C[Black is alive, but White managed to cut off the upper part. You can do better than this.])
(;B[cf];W[bi])
(;B[ak];W[cf]
(;B[bi];W[ap])
(;B[ap];W[bi])
(;B[df];W[bi])
(;B[bd];W[bi]))))
(;B[bi];W[al]
(;B[ak];W[ap]LB[al:A]C[If Black plays A White can capture all stones])
(;B[bj];W[ak])
(;B[af];W[ap]))
(;B[ak];W[ap]C[]
(;B[af];W[al])
(;B[bi];W[al])
(;B[al];W[bi])
(;B[bd];W[al])
(;B[cf];W[al]))
(;B[af];W[ap]LB[al:A]C[Black can't play A because of damezumari])
(;B[bd];W[bi]TR[am]TR[an]TR[ao]TR[bo]TR[bp]C[This also captures the marked stones.])
(;B[cf];W[bi]C[This also capturesd the marked stones.]TR[am]TR[an]TR[ao]TR[bo]TR[bp]))
(;W[al]C[]
(;B[ak];W[aq]
(;B[af]C[RIGHT])
(;B[al];W[ap];B[af]C[RIGHT])
(;B[bi];W[ap])
(;B[bd];W[ap]
(;B[al];W[bi])
(;B[bi];W[al])
(;B[af];W[al])
(;B[cf];W[al])
(;B[ad];W[al]))
(;B[cf];W[ap]
(;B[al];W[bi])
(;B[bi];W[al])
(;B[af];W[al])
(;B[bd];W[al])))
(;B[bi];W[ap])
(;B[af];W[ak])
(;B[bd];W[ak])
(;B[cf];W[ak]))
(;W[af];B[bd]C[RIGHT]))
(;B[bi];W[aj])
(;B[ak];W[bi]C[]
(;B[af];W[aj])
(;B[aj];W[af])
(;B[al];W[af])
(;B[bd];W[aj]))
(;B[af];W[ak]
(;B[bi];W[al])
(;B[aj];W[al])
(;B[al];W[ap]))
(;B[al];W[aj]
(;B[af];W[bi])
(;B[ak];W[bi])
(;B[cf];W[af])
(;B[bd];W[bi]))
(;B[bd];W[aj]
(;B[ad];W[bi])
(;B[af];W[bi])
(;B[ak];W[bi])
(;B[al];W[bi])
(;B[cf];W[bi]))
(;B[aq];W[aj]
(;B[af];W[bi])
(;B[cf];W[af])
(;B[ak];W[bi])
(;B[br];W[af])
(;B[al];W[af]))
(;B[cf];W[bi]C[]
(;B[af];W[aj])
(;B[aj];W[af])
(;B[ak];W[af])
(;B[al];W[af])
(;B[bd];W[aj])))