(;SZ[4]AB[ca]AB[cb]AB[cc]AB[cd]AW[ba]AW[bb]AW[bc]AP[goproblems]
(;B[ac];W[ab];B[bd];W[ad]C[The ko is nothing to White. Black wins.RIGHT])
(;B[bd]
(;W[db]
(;B[dc]C[Black lives.RIGHT])
(;B[ac]C[RIGHT]))
(;W[dc]
(;B[db]C[Black lives.RIGHT])
(;B[ac]C[RIGHT])))
(;B[db];W[bd]C[Both groups are alive, and Black doesn't win.])
(;B[dc];W[bd]C[Both groups are alive, and Black doesn't win.])
(;B[ab]
(;W[bd];B[ac]C[RIGHT])
(;W[ac];B[bd]C[RIGHT])))