(;SZ[9]AW[bd]AW[cd]AW[dd]AW[ed]AW[ae]AW[ee]AW[bf]AW[ef]AW[eg]AW[dh]AW[eh]AB[be]AB[ce]AB[de]AB[df]AB[bg]AB[cg]AB[dg]AB[ch]AB[ci]C[Black to move]GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]RU[Japanese]KM[0.00]GN[problem] (;B[ah] (;W[bi] (;B[af];W[ag] (;B[cf]C[];W[ad];B[af]C[RIGHT]) (;B[ad];W[ac] (;B[cf];W[ad];B[af]C[Yeah, right.RIGHT]) (;B[af]C[];W[cc]TR[dc]C[Think it is ko? Now let's assume that White has an absolutely huge threat at C7 that you must answer at D7. To help you appreciate the threat I forced that move. Please answer the huge threat at D7.FORCE];B[dc];W[ag]C[You happen to have a ko threat at E7 that is somewhat smaller than the group. Play E7 if you think you need it.]TR[ec] (;B[ec];W[af]C[Sorry, you died. But now at least you can follow up on your somewhat smaller threat.]) (;B[cf]C[Bingo! It was not ko after all.RIGHT])))) (;B[cf];W[af]) (;B[ag];W[af]) (;B[ad];W[af])) (;W[af];B[bi]C[check out the other variationRIGHT])) (;B[ag];W[af]C[black is reduced into dead shape]) (;B[af];W[ag] (;B[ah];W[bi] (;B[af]C[KO there is a better way]) (;B[cf]C[];W[ad];B[af]C[RIGHT]) (;B[ad];W[ac] (;B[cf];W[ad];B[af]C[Yeah, right.RIGHT]) (;B[af]C[];W[cc]TR[dc]C[Think it is ko? Now let's assume that White has an absolutely huge threat at C7 that you must answer at D7. To help you appreciate the threat I forced that move. Please answer the huge threat at D7.FORCE];B[dc];W[ag]C[You happen to have a ko threat at E7 that is somewhat smaller than the group. Play E7 if you think you need it.]TR[ec] (;B[ec];W[af]C[Sorry, you died. But now at least you can follow up on your somewhat smaller threat.]) (;B[cf]C[Bingo! It was not ko after all.RIGHT])))) (;B[cf];W[ah] (;B[af]C[Ko]) (;B[bh];W[af]) (;B[ad];W[af])) (;B[ad];W[af]) (;B[bi];W[ah])) (;B[bh];W[ag] (;B[ah];W[af]) (;B[cf];W[af])) (;B[cf];W[af] (;B[ag];W[ad]) (;B[ah];W[bi]) (;B[bi];W[ah])) (;B[bi];W[ah] (;B[ag];W[af]) (;B[cf];W[af]) (;B[af];W[ag])) (;B[ai];W[ag]) (;B[ad];W[af] (;B[ah];W[bi]) (;B[ag];W[ac]) (;B[cf];W[ac] (;B[ah];W[bi]) (;B[bi];W[ah]) (;B[ag];W[ad])) (;B[bi];W[ah])))