The game continued with BA, WB, BC, WD. But what if black cuts with D instead, which gives the problem position? How should white answer this?!
(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]
RU[Japanese]SZ[19]KM[0.00]TM[]
PW[Weiß]PB[Schwarz]AW[mb][nb][ob][jc][lc][pc][qc][je][kf][kg][mg][kh][lh][mh]AB[hb][kb][lb][gc][mc][nc][oc][gd][pd][ge][ie][ke][pe][if][jf][lf][mf][pf][lg][ng][pg]LB[jb:C][kc:B][ld:A][ke:D]PL[W]
(;W[md]CR[md]
(;B[kc]CR[kc]
;W[le]LB[kd:B][nf:A]CR[le]C[White can play A or B next RIGHT CHOICE])
(;B[ne]CR[ne]
(;W[kd]CR[kd]
;B[jd]CR[jd]
;W[jb]CR[jb]C[White captures the two black stones RIGHT CHOICE])
(;W[jb]CR[jb]
;B[kc]CR[kc]
;W[kd]CR[kd]
;B[jd]CR[jd]
;W[ld]CR[ld]C[White captures the black stones RIGHT CHOICE])))
(;W[jb]CR[jb]
;B[kc]CR[kc]
;W[kd]CR[kd]
;B[jd]CR[jd]
(;W[ka]CR[ka]
;B[ld]CR[ld]
;W[la]CR[la]C[This is not good enough for white])
(;W[ld]CR[ld]
;B[md]LB[md:A][ne:B]C[In the solution, the WA - BB exchange is in place,so white wins the semeai, but in this variation black simply captures white]))
(;W[kc]CR[kc]
;B[jb]CR[jb]C[After this exchange, white can't do anything]
(;W[md]CR[md]
;B[ne]CR[ne])
(;W[le]CR[le]
;B[jd]CR[jd]
;W[nf]CR[nf]
;B[me]CR[me]
;W[md]CR[md]
;B[ld]CR[ld]))
(;W[ld]CR[ld]
;B[kc]CR[kc]
(;W[kd]CR[kd]
;B[jd]CR[jd]
;W[le]CR[le]
;B[je]CR[je])
(;W[le]CR[le]
;B[kd]CR[kd]
;W[nf]CR[nf]
;B[me]CR[me])
(;W[nf]CR[nf]
;B[kd]CR[kd]
;W[md]CR[md]
;B[ne]CR[ne]))
(;W[le]CR[le]
;B[jd]CR[jd]
;W[md]CR[md]
;B[ne]CR[ne]
;W[kd]CR[kd]
;B[je]CR[je]
;W[jb]CR[jb]
;B[kc]CR[kc]
;W[ka]CR[ka]
;B[ld]CR[ld]
;W[la]CR[la]C[This is not good enough for white]))