(;
GM[1]
SZ[19]
AW[hc][ld][qd][pf][qj]
AB[dc][ce][nd][oc][qb]
C[Problem 46. Black to play.  

White's stones at the top are nicely balanced, but she is still vulnerable to an invasion. Where should Black invade ? ]
;B[jc]
TE[2]
C[Correct Answer.  

Black 1, in the middle of the three-space extension, is the vital point. ]
;W[jd]
C[White 2 is the best response, but ... ]
;B[kc];W[kd];B[lc];W[ic];B[md]
C[... Black links up with the moves to 7. <= ]
)
)