(;AW[ca]AW[fa]AW[fb]AW[ec]AW[gc]AW[cd]AW[dd]AW[ed]AW[ae]AW[be]AW[de]AB[ea]AB[bb]AB[db]AB[eb]AB[ac]AB[cc]AB[dc]AB[ad]AB[bd]TR[ca]C[Black did not answer the marked stone. What can white do now?]PL[W]
(;W[ba]
(;B[ab]
(;W[cb]C[sekiRIGHT])
(;W[aa];B[cb]C[Actually, black's last move is not even necessary; it is only shown for clarity.])
(;W[da];B[cb]C[Actually, black's last move is not even necessary. It is only shown for clarity.]))
(;B[cb];W[ab]C[Ko for the whole group; this usually is worse for black.]))
(;W[aa];B[ba])
(;W[ab];B[aa]
(;W[ba];B[ab])
(;W[cb];B[ba]C[Actually, black's last move is not even necessary, it's only shown for clarity.]))
(;W[cb];B[ba])
(;W[da];B[ba]))