(;
GM[1]
SZ[19]
AW[dd][gc][dj][cn][dp][po][pn][qn][qj][oj]
AB[cf][fq][jp][op][pq][qp][qo][qh][qd][od][kc]
TR[cf]
C[Problem 88. White to play.  

Black has entered White's sphere of influence with the marked stone. How should White respond ? ]
(;W[cd]
TE[2]
C[Correct Answer.  

White 1 not only secures the corner, it also attacks the black stone. ]
(;B[ch]
C[If Black extends to 2, ... ]
;W[cj]
C[... White makes an iron pillar with 3. Black's stones are still under attack. <= ]
)
(;B[ef]
LB[cd:1]
C[Variation.  

If Black responds to White 1 by jumping to 2, ... ]
;W[dg]
C[... White will peep with 3, ... ]
;B[df];W[ge]
C[... then jump to 5. Black's stones are still under attack and an invasion into White's corner in the upper left is no longer possible. <= ]
))
(;W[ce]
C[Failure.  

Attacking with 1 ... ]
;B[df];W[dh]
C[... and 3 is also possible. ]
(;B[ff]
C[If Black jumps to 4, ... ]
;W[be]
LB[ff:4]
C[... White secures the corner with 5. This result is also good for White. But Black will not play 4. <= ]
)
(;B[ch]
LB[dh:3]
C[Black makes sabaki.  

After White 3, Black can attach with 4 ... ]
;W[ci];B[eh]
C[... and 6, ... ]
;W[ei];B[dg]
C[... then atari with 8. ]
;W[di]
C[If White connects with 9, ... ]
;B[fh]
C[... Black can extend to 10. Black has a more resilient shape than in the Correct Answer, so this result is not as good for White. <= ]
))
)