(;
GM[1]
SZ[19]
AW[dc][cp][cn][dq][eq][qn][qk][nc][kd]
AB[ep][fq][fp][jp][pq][qp][qi][pd][pc]
LB[pc:B][nc:A][kd:C]
C[Problem 11. Black to play.  

White has just extended to C. How should Black continue ? ]
;B[on]
TE[2]
C[Correct Answer.  

Black should cap at 1, ... ]
;W[ok]
C[... forcing White to jump to 2. ]
;B[oi]
C[This induces Black to reinforce his moyo above with 3. ]
;W[mk]
C[Jumping to 4 is natural. ]
;B[ic]
C[Black now invades the top with 5. ]
(;W[gc]
C[White has to play forcefully and pincer with 6. ]
;B[ie];W[jc]
C[If White attaches with 8, ... ]
;B[jb];W[kb];B[jd];W[kc];B[ke];W[le];B[kf];W[lf];B[lg]
C[... Black presses the white stones with the sequence to 17. ]
;W[ne]
C[White then makes shape with 18 and ... ]
;B[of]
C[... Black secures the upper right with 19.  <= ]
)
(;W[je]
LB[ic:5]
C[Variation.  

White 6 here is another response to Black 5. ]
;B[he]
C[Black jumps to 7 and ... ]
;W[gc]
C[... White pincers with 8. ]
;B[gd];W[fc];B[hc]
LB[gd:9]
C[Black makes shape with 9 and 11, after which ... ]
;W[de];B[ig];W[kg];B[ii]
LB[ig:13]
C[... Black attacks with 13 and 15. ]
(;W[ki]
C[After White 16, ... ]
;B[ne]
C[... Black secures the territory on the right with 17.  <= ]
)
(;W[ne]
C[If White 12 here, ... ]
;B[of]
C[... Black will play 17 here.  <= ]
))
)