This is an extremely basic example of how your opponents best move is often your best move.
(;AP[goproblems]AB[ra]AB[rb]AB[rc]AB[qd]AB[pd]AB[od]AB[nc]AB[mc]AB[lc]AB[kb]AB[jb]AW[qa]AW[qb]AW[pb]AW[ob]AW[oa]AW[nb]AW[mb]C[Black to kill.](;B[ma]C[];W[la]C[White is dead and would only play additional moves as ko threats.](;B[lb]C[RIGHT])(;B[ka];W[lb])(;B[oc];W[lb])(;B[pc];W[lb])(;B[qc];W[lb]))(;B[la];W[ma])(;B[lb];W[ma])(;B[na];W[ma])(;B[oc];W[ma])(;B[pc];W[ma])(;B[qc];W[ma])(;B[ka];W[ma]))