(;
GM[1]
SZ[19]
AW[cf][dk][dn][cn][bm][ho][hq][nq][ol][ql][qc][qd][rf][rg][nc]
AB[dp][pd][pp][dd][gc][bn][bo][co][fp][fq][fn][pn][nn][qj][pc][pe][qf][qg]
TR[rg]
C[Problem 121. Black to play.  

White tries to expand her corner by crawling with the marked stone. How should Black counter this move ? ]
(;B[qb]
TE[2]
C[Correct Answer.  

White's stones in the corner are thin, so Black can get massive thickness and confine White to the corner by playing the hane of 1. ]
;W[qe];B[rc];W[rd];B[sd];W[re];B[qh];W[rb];B[pb];W[ra]
LB[sb:A]
C[The sequence to White 10 is inevitable. White cannot omit 10 because Black is threatening to start a ko with A. ]
;B[lc]
C[Finally, Black pincers with 11 and his moyo at the top is nearly impregnable. ]
;W[ml]
C[Next, White must run away with B, since a black move there would completely crush her. <= ]
)
(;B[qh]
C[How the game continued.  

Black extended with 1, but ... ]
;W[pb];B[ob];W[qb]
LB[pb:2]
C[... this enabled White to secure the corner with the hane and connection of 2 and 4. ]
;B[oc]
C[White ended in sente, so ... ]
;W[rn]
C[... she took her opportunity to stabilise her stones on the lower right ... ]
;B[qo];W[ro];B[rp];W[qk]
C[... with the sequence to 10. <= ]
)
)