(;
GM[1]
SZ[19]
AW[cn][cc][cb][dd][de][ee][ef][eg][cf][bf][bg][ch][fd][qc][qe][qh][rn][po][pq][jq]
AB[cp][eq][bb][bc][cd][ce][be][df][cg][dc][ec][ed][fe][gd][lc][oc][qj][qm][rm][ff]
TR[cn]
C[Problem 91. Black to play.  

White has just made a wide extension from her thickness above with the marked stone. Where should Black play next ? ]
(;B[fg]
LB[eh:A]
TR[cn]

TE[2]
C[Correct Answer.  

Black 1 is a strong move because it expands Black's moyo at the top and threatens to force at A. Instead of playing the marked stone, White should have turned at 1. <= ]
)
(;B[hq]
C[Failure.  

Responding to the marked stone by extending to 1 is not good. ]
;W[fg]
LB[cm:A]
TR[cn]
C[White turns at 2. If White played the marked stone at 2, Black would extend to A, neutralising White's thickness above. <= ]
)
)