(;
GM[1]
SZ[19]
AW[ec][dc][cd][cf][cg][qc][oc][re][qp][pq][np][on][om][pn][qn][rn][pl][nl][ml][mm][lj]
AB[df][dg][dh][ed][fc][gd][mc][ne][pe][ep][jp][po][qo][rm][qm][pm][ol][ok][pk][nk][nm]
C[Problem 73. Black to play.  

All of White's groups are safe. What should Black do ? ]
(;B[kg]
TE[2]
C[Correct Answer.  

Since there is nothing to attack, now is a good time for Black to reinforce his moyo at the top with 1. Black can expect a large territory here. <= ]
)
(;B[mk]
C[Failure.  

In the game, Black cut trough with 1 ... ]
;W[lk];B[ll]
C[... and 3, hoping to isolate the white stones in the center and attack them. ]
;W[kl];B[lm];W[mn];B[km]
C[But the black stones became heavy and vulnerable. <= ]
)
)