(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2] RU[Japanese]SZ[19]KM[0.00]TM[] PW[White]PB[Black]AW[an][bn][cn][dn][do][eo][fo][go][ho][io][dp][cq]AB[ao][bo][co][cp][ep][fp][gp][hp][ip][dq]LB[dp:A][cq:B]C[White pushed with A, Black played elsewhere, and White cut with B. What can Black do?] (;B[bq]CR[bq] ;W[cr]CR[cr] (;B[br]CR[br] ;W[dr]CR[dr] (;B[eq]CR[eq] ;W[ap]CR[ap] (;B[bp]CR[bp] ;W[bs]CR[bs] (;B[ar]CR[ar] ;W[cs]CR[cs] ;B[er]LB[dp:A]CR[er]C[RIGHT White's push at A only generates potential ko threats.]) (;B[er]CR[er] ;W[ar]CR[ar]C[Black has given up too much.]) (;B[as]CR[as] ;W[ar]CR[ar]C[Black has given up too much.]) (;B[cs]CR[cs] ;W[ar]CR[ar]C[White is happy with a ko.])) (;B[er]CR[er] ;W[bp]CR[bp]C[Black has given up too much.])) (;B[er]CR[er] ;W[eq]CR[eq] ;B[fq]CR[fq] ;W[ap]CR[ap]C[White is happy with ko and an internal ko threat.]) (;B[bs]CR[bs] ;W[eq]CR[eq]C[Black lives in the corner, but has given too much by letting White in.]) (;B[ap]CR[ap] ;W[eq]CR[eq]C[Black lives in the corner, but has given up too much letting White in.])) (;B[dr]CR[dr] ;W[br]CR[br] (;B[cs]CR[cs] ;W[ar]CR[ar] ;B[bs]CR[bs] ;W[ap]CR[ap]C[Black has given up too much.]) (;B[ar]CR[ar] ;W[ap]CR[ap]C[Black has given up too much.])) (;B[ar]CR[ar] ;W[ap]CR[ap] ;B[bp]CR[bp] ;W[br]CR[br] ;B[aq]CR[aq] ;W[dr]CR[dr] ;B[er]CR[er] ;W[eq]CR[eq] ;B[fq]CR[fq] ;W[bs]CR[bs]C[White is ahead in liberties and takes the corner.]) (;B[cs]CR[cs] ;W[br]CR[br] ;B[dr]CR[dr] ;W[ar]CR[ar] ;B[bs]CR[bs] ;W[ap]CR[ap]C[Black has given up too much.])) (;B[cr]CR[cr] ;W[bq]CR[bq] (;B[br]CR[br] ;W[dr]CR[dr] (;B[eq]CR[eq] ;W[ar]CR[ar] (;B[bp]CR[bp] ;W[ap]CR[ap]C[Black has given up too much.]) (;B[aq]CR[aq] ;W[ap]CR[ap]C[Black has given up too much.])) (;B[er]CR[er] ;W[eq]CR[eq] (;B[fq]CR[fq] ;W[dq]CR[dq]C[Black has given up too much.]) (;B[ds]CR[ds] ;W[dq]CR[dq] ;B[fr]CR[fr] ;W[fq]CR[fq]C[The four black stones can not escape; Black has given up too much.]))) (;B[dr]CR[dr] ;W[br]CR[br]C[Black has given up too much.])))