(;
GM[1]
SZ[19]
AW[cd][fc][ch][eh][el][er][ol][pm][qm][qn][qo][qp][qq]
AB[dp][pd][pp][cj][ej][cl][jp][pq][po][pn][om][nm][pl][pk]
LB[er:1]
C[Problem 146. Black to play.  

White plays a low approach with 1, aiming to disrupt Black's moyo at the bottom. How should Black respond ? ]
(;B[dq]
TR[er]

TE[2]
C[Correct Answer.  

Extending to Black 1 is a standard response to the low approach of the marked white stone. ]
;W[hq]
C[White responds by jumping lightly to 2 ... ]
;B[jq];W[ho]
C[... and 4, but ... ]
;B[gp]
C[... Black launches a severe attack ... ]
;W[hp];B[in];W[hn];B[im]
C[... with the sequence to 9. ]
;W[gl]
C[White's stones are still not secure and Black has expanded his moyo in the bottom right. Meanwhile, his territory on the lower left side is still intact and White must worry about her endangered stones. <= ]
)
(;B[fq]
C[Failure.  

Building thickness with the sequence from 1 ... ]
;W[fr];B[gq];W[cq];B[dq];W[dr];B[cp]
C[... to 7, ... ]
;W[bq];B[gi]
C[... then expanding the moyo with 9, is an interesting strategy, but ... ]
;W[jj]
C[... White 10 is the key point for wiping out  Black's moyo. White's gain in the corner is too big with respect to what Black can expect to gain from his moyo. Moreover, White can make incursions into Black's moyo on the left and the right from her corner. ]
)
)