(;
GM[1]
SZ[19]
AW[dc][hd][di][dn][dp][pq][qq][nq][nr]
AB[jd][pd][pj][gp][lq][mo][op][pp][qp]
C[Problem 50. Black to play.  

White has countered Black's sanren-sei opening with a Chinese opening. Where should Black play ? ]
(;B[if]
TE[2]
C[Correct Answer.  

Black 1 is the focal point of the two moyos. ]
;W[gf]
C[If White defends her moyo with 2, ... ]
;B[hh]
C[... Black keeps advancing with 3, making the scale of his moyo even greater while diminishing the scale of White's. <= ]
)
(;B[gm]
C[Failure.  

Black 1 is also a good point because it strengthens his thin position at the bottom. However, ... ]
;W[if]
C[... White takes the vital point of 2 and ... ]
;B[kf];W[jh]
C[... marches into Black's sphere of influence with 4. <= ]
)
)