(;
GM[1]
SZ[19]
AW[ec][ed][qq][pq][op][kq][cp][dp][dn][ep][fp][eq][gq][hq][bh][ci][cg][dg][ef][ff][di]
AB[dc][cd][ic][pd][pm][qp][ro][rq][fq][gp][fo][fr][er][dr][cq][df][cf][bf][bg][eg][eh][gh]
LB[eg:A][ff:B][eh:C][di:D][gh:E]
C[Problem 100. White to play.  

Black plays the sequence to E, isolating the white stones at the top. But Black's stones in the center are also weak. What should White do ?  

[You will find a supplement to this Problem Diagram as "Problem 144"] ]
;W[ie]
TE[2]
C[Correct Answer.  

White should attack the black stone at the top by capping with 1. ]
(;B[kd]
C[If Black responds with 2, ]
;W[ih]
C[... White goes on the offensive against the three black stones in the center with 3 ... ]
;B[fj];W[ik]
C[... and 5. Black is in trouble. ]
(;B[dk]
TR[ik]
C[After White plays the marked stone, Black might try to attack the white stones in the upper left by invading with 6. ]
;W[ck];B[cl];W[dl];B[cj];W[bk];B[el];W[dm];B[dj];W[bj]
C[However, White easily links up with the sequence to 15. ]
;B[fl];W[ej];B[ek];W[ei];B[fi];W[gk]
C[After peeping at 21, ... ]
;B[fk];W[hg]
C[... White makes a reinforcing move with 23 and the black stones are trapped within White's sphere of influence. <= ]
)
(;B[hg]
C[Variation.  

Since White is thin in the center, Black can escape with 6 ... ]
;W[ke];B[ig]
LB[ke:5]
C[... and 8, but Blacks stones become at the top become  vulnerable after White 5. Next ... ]
;W[jd]
C[... White plays 9. ]
;B[he]
C[If Black tries to capture the white stones in the top left by attaching with 10, ]
;W[hd];B[id];W[hf];B[ge];W[gf];B[if];W[je];B[gd];W[jc];B[gc];W[ib];B[hc];W[fb];B[gb];W[ga];B[ha];W[fa];B[hb];W[jb]
C[... he will find himself caught up in a capturing race that he has no hope of winning. This would be a disaster for Black. <= ]
))
(;B[ih]
LB[ie:1]
C[Variation.  

If Black answers the cap of White 1 by jumping to 2, ... ]
;W[jc]
C[... White will attack the top ... ]
;B[jb];W[jd];B[kb];W[lc];B[lb];W[mc];B[mb];W[hc];B[hb];W[id];B[ib];W[nc]
C[... with the sequence to 15. ]
;B[ob]
C[After Black defends the corner with 16, ... ]
;W[hi];B[hh];W[fj];B[kh];W[jj]
C[... White maps out a moyo in the lower left with the sequence to 21. <= ]
)
)