(;AW[eb]AW[db]AW[cb]AW[bb]AW[ac]AW[cc]AW[ea]AB[fa]AB[fb]AB[ec]AB[dc]AB[gc]AB[cd]AB[bd]AB[bc]AB[be]C[Black to kill.]AP[goproblems]
(;B[ab]
(;W[aa]C[CHOICE]
(;B[ca]C[RIGHT])
(;B[ad];W[ca];B[ab]C[Only ko.]))
(;W[ca]C[CHOICE]
(;B[ad];W[aa]
(;B[ac]C[RIGHT])
(;B[ba]C[White should not be able to win this.RIGHT]))
(;B[aa];W[ba];B[ab];W[aa]C[RIGHT])))
(;B[ba];W[ca]
(;B[ab];W[aa])
(;B[aa];W[ab])
(;B[ad];W[ab]))
(;B[ca]
(;W[ba]C[CHOICE];B[ab]C[RIGHT])
(;W[ab]C[CHOICE];B[ba]C[RIGHT]))
(;B[aa];W[ab])
(;B[ad];W[ab]))