(;SZ[13]AB[ac]AB[bb]AB[cb]AB[db]AB[eb]AB[ea]AW[ca]AW[fa]AW[fb]AW[fd]AW[ec]AW[dc]AW[cc]AW[bd]AW[ad]AP[goproblems]
(;B[bc];W[ba];B[aa];W[ab]C[Just a ko, black can do betterCHOICE])
(;B[ba];W[bc];B[ab]C[RIGHT])
(;B[da];W[bc]
(;B[ab];W[ba]C[CHOICE])
(;B[ba];W[ab]C[CHOICE]))
(;B[ab];W[ba]C[CHOICE])
(;B[aa];W[bc]C[CHOICE]))