Note: This is an endgame problem. It is not enough to just live (if possible), you need to get the best result possible.
(;AB[rb]AB[rc]AB[rd]AB[qe]AB[qf]AB[qg]AB[qh]AB[rh]AB[sh]AW[si]AW[ri]AW[qi]AW[pi]AW[ph]AW[pg]AW[pf]AW[pe]AW[qd]AW[qc]AW[qb]AW[od]AW[ra]AW[sb]AW[ob]TR[sb]C[White just played the marked move; what is black's best answer.]AP[goproblems]
(;B[rf];W[sc]
(;B[sd]C[White cannot do anything useful; Black can capture at T19 later.RIGHT])
(;B[se];W[qa]C[Almost correct, but you could get a little bit more.])
(;B[sg];W[sd]
(;B[se];W[re];B[rd]C[Losing the three stones is not necessary.])
(;B[re];W[se]C[You're dead.])))
(;B[re];W[sf]
(;B[sc];W[se]
(;B[rf];W[sg]C[Seki is not best.])
(;B[sg];W[rf]C[Seki is not best])
(;B[sa];W[qa]C[This is only seki, you could have lived with points.]))
(;B[se];W[sc]C[dead])
(;B[rf];W[sg];B[sc];W[se]C[Seki is not the best])
(;B[sg];W[rf];B[sc];W[se]C[Seki is not the best.]))
(;B[se];W[rf]
(;B[sc];W[re];B[sa];W[sg]C[That's not even ko.])
(;B[sf];W[sc]
(;B[rg]C[Close, but you could have done slightly better.])
(;B[sd];W[rg];B[sa];W[sb]))
(;B[rg];W[sc]
(;B[sf]C[Close, but you could have done slightly better.])
(;B[sd];W[sf];B[sa];W[sb]))
(;B[re];W[sc]C[dead]))
(;B[sf];W[re]
(;B[sd];W[rf]C[dead])
(;B[se];W[sc]
(;B[rf]C[Close, but you could have done better.])
(;B[sd]C[White cannot do anything useful, whereas black can capture at T19 at any moment.RIGHT]))
(;B[rf];W[sc];B[se]C[Close, but you could have done better.]))
(;B[sc];W[re]
(;B[sa];W[rf]C[Not even ko])
(;B[se];W[sd]))
(;B[sd];W[rf]
(;B[sf];W[re]C[Dead by damezumari])
(;B[re];W[sf]))
(;B[qa]C[NOTTHIS]))