(;
GM[1]
SZ[19]
AW[jc][nc][nd]
AB[dd][hc][oc][pd][pf]
C[Problem 25. Black to play.  

White has made an ideal extension from her two stones on the right. However, it is still possible to invade this position. Where does  Black play ? ]
;B[lc]
TE[2]
C[Correct Answer.  

Black should invade at 1. ]
(;W[ld]
C[If White attaches at 2, ... ]
;B[kc];W[kd];B[jb]
LB[kc:3]
C[... Black links up to his allies on the left with 3 and 5. <= ]
)
(;W[lb]
C[Variation.  

If White attached underneath with 2, ... ]
;B[mb];W[mc];B[kb];W[ld];B[kc]
(;W[kd];B[nb]
C[... Black would play the moves to 9. <= ]
)
(;W[nb]
C[If White 8 here, ... ]
;B[kd]
C[... Black plays 9. Either way, Black is satisfied. <= ]
))
)