(;
GM[1]
SZ[19]
AW[cb][dc][eb][fd][kc][oc][di][cj][cn][co][dp][cq][cr][rp][rq][qq][pq][nq][qn]
AB[qd][pe][cc][cd][de][ch][cl][el][bn][dr][fq][iq][op][pp][qp][qo][ro][pl][pi]
TR[di][cj]
C[Problem 99. Black to play.  

How should Black attack the two marked white stones ? ]
(;B[fj]
TE[2]
C[Correct Answer.  

Black should drive White towards the top with the knight's move of 1. ]
;W[dh]
C[After exchanging 2 ... ]
;B[cg]
C[... for 3, ... ]
;W[fh]
C[... White jumps to 4. ]
;B[hi]
C[Black keeps up the attack with 5, and, ... ]
;W[ff]
C[... after White 6, ... ]
;B[fn]
LB[jh:B][hg:A]
C[... jumps to 7 to make a moyo in the lower left. If White A, Black will jump to B. <= ]
)
(;B[ff]
C[Failure.  

Black 1 certainly keeps the white stones from linking up to their allies at the top, but ... ]
;W[dh];B[cg];W[gi];B[hk];W[ii];B[jk];W[ki]
LB[fh:C][gg:B][ef:A]
C[... White easily escapes into the center with the sequence to 8. Black's prospects for making a moyo at the bottom are no longer realistic because Black must defend against White A. If Black B, White C keeps the threat A viable. <= ]
)
)