11/2/01 Added unkx80's variation.
11/1/01 Added a variation suggested by hello.
10/31/01 Added a "much more interesting answer for white" suggested by wol.
(;SZ[19]AW[eb]AW[dc]AW[ec]AW[cd]AW[ae]AW[be]AW[ce]AB[cb]AB[db]AB[ac]AB[cc]AB[bd]C[Black to play and live. (Don't let White get a Ko).]GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]RU[Japanese]KM[0.00]TM[]
(;B[ba]
(;W[bc]
(;B[bb]
(;W[da];B[ad]C[CHOICERIGHT])
(;W[ad];B[da];W[bc];B[ab]C[CHOICERIGHT]))
(;B[ab]
(;W[ad];B[da]C[CHOICERIGHT])
(;W[da];B[ad]C[CHOICERIGHT]))
(;B[da];W[ad]
(;B[bb];W[ab])
(;B[ab]C[RIGHT])))
(;W[da];B[ab]C[Black 1 is the vital point to have two eyes.RIGHT])
(;W[ad];B[bc]C[Black now has the option to make two eyes by playing D19 or A18RIGHT]LB[da:A]LB[ab:B]))
(;B[bb];W[ad]
(;B[aa];W[bc]C[If Black 1, then White 2 gets a Ko.])
(;B[bc];W[da]))
(;B[ad];W[ab])
(;B[ab];W[ba]
(;B[bb];W[ad])
(;B[ad];W[bb]))
(;B[da];W[ba];B[bb];W[ad]
(;B[aa];W[ab]C[Dead by double ko. You need to win them both to live, but if you take one White takes the other.]MA[bd])
(;B[ca];W[aa])
(;B[bc];W[aa])))