(;AW[qb]AW[pb]AW[rc]AW[rd]AW[qd]AW[pc]AB[pd]AB[od]AB[oc]AB[ob]AB[oa]AW[pa]AB[qe]AB[re]AB[qf]AW[se]AB[sf]AW[sd]TR[sd]C[Whites last move was the marked stone, a mistake; it should have been at A. What can black do?]LB[sc:A]AP[goproblems] (;B[rb] (;W[ra]C[CHOICE];B[sb]C[This is a seki. White has no territory.RIGHT]) (;W[sb]C[CHOICE];B[ra]C[This is a seki. White has no territory.RIGHT])) (;B[sb];W[rb]C[White lives with territory.]) (;B[ra];W[rb]C[White lives with territory.]) (;B[sc];W[sb]C[White lives with territory.]) (;B[qa];W[ra]C[White lives with territory.]))