(;
GM[1]
SZ[19]
AW[de][df][cf][cj][cl][cm][cn][co][bp][qq][im][kn][mo][no][np][oq][op][pp][qn][pm][ql][rm][qh][pi][oi][nj][nk][mi][mh][li][ki][kh][pd][nc][kc]
AB[dc][fc][cd][ce][bm][bn][bo][cp][cq][do][eq][pq][pr][or][nq][mr][mp][lp][jo][rl][qj][mk][mj][lh][kg][lf][mg][ni][nh][oh][nf][of][og][qf][rd][qc]
TR[kc][nc][pd]
C[Problem 91. Black to play.  

How should Black attack the three marked stones ? ]
(;B[kb]
TE[2]
C[Correct Answer.  

Attaching with Black 1 in an interesting move.. Next ... ]
(;W[jb]
C[If White plays on the outside with 2, ... ]
;B[lc];W[lb];B[mb];W[ka];B[mc]
LB[hc:b][ic:A]
TR[pd][nc]
C[... Black will capture the two marked stones with the sequence to 7. Black is now threatening to kill the white stones by attacking at A, so White has to play B in gote to ensure that her stones are alive. <= ]
)
(;W[lb]
C[Variation.  

If White blocks on the inside with 2, ... ]
;B[jb]
C[... Black will draw back to 3. ]
;W[ld]
C[After 4, Black continues to attack the white stones with 5, while building territory in the top left, ... ]
;B[id];W[pc]
C[... so White has to play 6 to secure her isolated stones. Again, Black ends in sente. <= ]
))
(;B[ic]
C[Failure.  

Black 1 is the move many players would make, but ... ]
;W[jc]
C[... White easily makes a living group with 2 ... ]
;B[id];W[pc]
C[... and 4. <= ]
)
(;B[ob]
C[Failure.  

If Black slides to 1, ... ]
;W[hc]
C[... White would extend to 2, and again her stones are alive. <= ]
)
)