(;
GM[1]
SZ[19]
AW[fq][lp][pm][nj][qf][ko][ln][mo][ch][eh][dl][cj]
AB[jp][jd][pj][dj][dp][pd][pp][dd][dn][np][nf][nd][lq][kp][mp][cf][fj]
LB[dl:1][cj:3][fj:2]
C[Problem 20. Black to play.  

In the game in Problem 16, White exchanged 1 for 2, then attached at 3, aiming to link up his stones on the left side. How should Black deal with this move ? ]
(;B[di]
TE[2]
C[Correct Answer.  

Black should let White link up along the side and push through in the center with 1 ... ]
;W[ci];B[dh]
C[... and 3. ]
;W[dg];B[cg];W[dk];B[fi]
C[With the sequence to 7, White manages to link up some of her stones and get a small bit of territory on the left, but, in return, Black gets a thick position and territory in the upper left. <= ]
)
(;B[ck]
C[How the game continued.  

The hane of Black 1 was a black move. ]
;W[dk]
C[After White cut with 2, ... ]
;B[di]
C[... Black found his stones short of liberties after 3 ... ]
;W[ci]
(;B[dh]
C[... and 5, so ... ]
;W[dg];B[fi]
C[... he had to defend at 7 ... ]
;W[cg]
C[... instead of being able to cut at 8. See Problem 24 for the continuation of this game. <= ]
)
(;B[fi]
LB[dh:@][dg:6]
C[The Black @ - White 6 exchange was bad. Black should have simply played at 5 here. <= ]
))
)