(;
GM[1]
SZ[19]
AW[jc][nc][nd][od]
AB[dd][hc][oc][pc][qd][qf]
C[Problem 54. Black to play.  

Where should Black invade White's formation at the top ? ]
;B[lc]
TE[2]
C[Correct Answer.  

Black 1 is the best move. ]
(;W[ld]
C[If White attaches at 2, ... ]
;B[lb]
C[... Black descends to 3 and ... ]
;W[kd];B[nb]
LB[jb:A]
C[... he can link either at 5 or at A. White is satisfied with her thickness. <= ]
)
(;W[kd]
C[Failure.  

The diagonal move of 2 is not good. ]
;B[ld]
C[Black pushes up with 3, ... ]
;W[le];B[lb]
LB[nb:B][jb:A]
C[... then descends to 5, enabling him to link up with A or B. White's stones are thin and vulnerable. <= ]
)
)