(;AB[dc]AW[de]AB[ee]AW[dd]AB[fc]AW[cc]AB[ec]AB[df]AB[cf]AW[bd]AW[db]AB[be]AB[bb]AB[eb]AW[cb]AB[ff]AW[cd]AB[eg]AW[ea]AB[gb]AB[bg]AP[goproblems] (;W[ab];B[ba] (;W[ad];B[bc] (;W[da]C[RIGHT]C[White can live in seki by playing A17, and if black plays there, he leaves a living shape for white to capture.RIGHT]) (;W[ca]C[This is not a seki, because white's main group is not connected to the liberty at A19.]) (;W[ac];B[da])) (;W[da];B[ad]) (;W[bc];B[ad]) (;W[ca];B[bc];W[ad]C[This is not a seki, because white's main group is not connected to the liberty at A19.]) (;W[ac];B[da]C[Not enough room for two eyes])) (;W[ba];B[ab] (;W[da];B[ad]) (;W[ac];B[da]) (;W[ad];B[da]) (;W[ae];B[da])) (;W[da];B[ba] (;W[ac];B[ab]C[Black kills by making an 'eye in the stomach']) (;W[ab];B[ac] (;W[ad];B[aa] (;W[bc];B[ab]) (;W[ca];B[ab])) (;W[bc];B[aa] (;W[ca];B[ab]) (;W[ad];B[ab])) (;W[ca];B[aa] (;W[ad];B[ab]) (;W[bc];B[ab]))) (;W[bc];B[ab]C[Black kills by making an 'eye in the stomach']) (;W[ad];B[ab]C[Black kills by making an 'eye in the stomach'])) (;W[ac];B[ba];W[da];B[ab]) (;W[ad];B[ab] (;W[da];B[ba]C[Black kills by making an 'eye in the stomach']) (;W[ba];B[da])))