In this game, black is doing well, after having killed the white group on the bottom. However, if he wants to win, then he needs to save his marked group. White just played triangle, attempting to live and isolate black's one-eyed group. How would you deal with this, as black?
(;AB[gb]AB[fc]AB[fd]AB[hc]AB[ib]AB[ic]AB[id]AB[ge]AB[he]AB[hf]AB[hg]AB[gg]AB[ig]AB[jg]AB[kg]AB[kh]AB[li]AB[lj]AB[kk]AB[jm]AB[jn]AB[in]AB[ef]AB[df]AB[cg]AB[fh]AB[eh]AB[ei]AB[ej]AB[ek]AB[fk]AB[dk]AB[ck]AB[cj]AB[bk]AB[cl]AB[bm]AB[an]AB[dm]AB[dn]AB[eo]AB[eq]AB[go]AB[fp]AB[ap]AB[bq]AB[br]AB[dr]AB[er]AB[fr]AB[fs]AB[gs]AB[hr]AB[ir]AB[jr]AB[is]AB[ko]AB[lo]AB[lp]AB[lq]AB[mq]AB[nr]AB[or]AB[oq]AB[pq]AB[pp]AB[ms]AB[qd]AB[rd]AB[se]AB[pe]AB[pf]AB[pg]AB[ph]AB[qg]AB[qj]AB[qk]AB[rl]AB[qm]AB[pm]AW[bn]AW[cn]AW[cm]AW[bp]AW[cp]AW[cq]AW[cr]AW[dq]AW[ar]AW[bs]AW[fq]AW[gq]AW[gr]AW[hp]AW[hq]AW[iq]AB[ho]AW[io]AW[jo]AW[jp]AW[kp]AW[kq]AW[kr]AW[js]AW[lr]AW[mr]AW[ls]AW[pr]AW[qr]AW[qq]AW[ro]AW[qn]AW[rm]AW[sn]AW[ql]AW[fj]AW[fi]AW[gh]AW[jh]AW[ii]AW[jj]AW[ki]AW[jk]AW[il]AW[hk]AW[gm]AW[em]AW[bj]AW[bi]AW[ci]AW[di]AW[dj]AW[bg]AW[cf]AW[ce]AW[dd]AW[ee]AW[fe]AW[ff]AW[fg]AW[ec]AW[eb]AW[fb]AW[ha]AW[gd]AW[jb]AW[jc]AW[jd]AW[ie]AW[if]AW[kf]AW[lg]AW[lh]AW[lc]AW[od]AW[pc]AW[qc]AW[qf]AW[qe]AW[re]AW[rg]AW[qh]AB[lk]AW[kj]AW[gl]AW[gj]TR[gj]MA[fd]MA[fc]MA[gb]MA[hc]MA[ib]MA[ic]MA[id]MA[he]MA[ge]MA[hf]MA[gg]MA[hg]MA[ig]MA[jg]MA[kg]MA[kh]AW[mb]AW[kd]AB[kl]C[See description.]AW[nf]AW[mk]AW[of]AB[gc]MA[gc]AW[pd]AW[hh]AP[goproblems]
(;B[lf]
(;W[jf]C[CHOICE]
(;B[mg];W[mh];B[nh];W[mi];B[mj];W[ni];B[oi];W[nj];B[nk];W[oj]
(;B[ok];W[pj]
(;B[pk]C[Good! Black lives easily. Hopefully white would not actually play this out in a real game. You were right not to attack the middle group - it was already alive.RIGHT])
(;B[pi]C[Good! Black lives easily. Hopefully white would not actually play this out in a real game. You were right not to attack the middle group - it was already alive.RIGHT])
(;B[ng];W[mf];B[le];W[pi]
(;B[qi];W[oh];B[rf];W[og])
(;B[rf];W[oh];B[og];W[me])
(;B[og];W[oe];B[rf];W[qi])))
(;B[pj];W[ok];B[ol];W[nl];B[pk];W[nk];B[nm]C[RIGHT]))
(;B[mh];W[mg])
(;B[mf];W[ng];B[mg];W[mh]
(;B[nh];W[mi]
(;B[mj];W[ni];B[oh];W[me])
(;B[ni];W[mj])
(;B[oe];W[me]))
(;B[le];W[nh])
(;B[me];W[nh]))
(;B[le];W[nh];B[mg];W[mh];B[ng];W[og];B[mf];W[oh]))
(;W[mf]C[CHOICE];B[je]
(;W[ke]C[];B[jf]C[Good! Black gets a second eye and lives. You were correct not to attack the middle group - it was already alive.RIGHT])
(;W[jf]C[];B[ke]C[Good! Black gets a second eye and lives. You were correct not to attack the middle group - it was already alive.RIGHT])))
(;B[jf];W[je])
(;B[je];W[jf]
(;B[lf]
(;W[ke]C[CHOICE];B[mg];W[mh];B[nh];W[mi];B[mj];W[ni];B[oi];W[nj];B[nk];W[oj]
(;B[ok];W[pj]
(;B[pi]C[Good! Black lives easily. Hopefully white would not actually play this out in a real game. You were right not to attack the middle group - it was already alive.RIGHT])
(;B[pk]C[Good! Black lives easily. Hopefully white would not actually play this out in a real game. You were right not to attack the middle group - it was already alive.RIGHT]))
(;B[pj];W[ok];B[ol];W[nl];B[pk];W[nk];B[nm]C[RIGHT]))
(;W[mf]C[];B[ke]C[Good! Black gets a second eye and lives. You were right not to attack the middle group - it was already alive.RIGHT]))
(;B[le];W[lf])
(;B[mf];W[lf]))
(;B[ke];W[lf]
(;B[jf];W[je])
(;B[je];W[jf]))
(;B[le];W[lf]
(;B[je];W[jf])
(;B[jf];W[je]))
(;B[hi];W[jf]
(;B[ih];W[gi])
(;B[hj];W[ij]))
(;B[ih];W[jf];B[hi];W[gi])
(;B[hj];W[jf]))