(;
GM[1]
SZ[19]
AW[pc][mc][ph][ql][pp]
AB[ce][dp][ne][qe][qn]
LB[dc:A][on:B][qq:C]
TR[ql]
C[Problem 117. Black to play.  

White has just pincered with the marked stone. Should Black answer it by jumping to B, invading at C or making a corner enclosure with A ? ]
(;B[on]
TE[2]
C[Correct Answer.  

Jumping to 1 is the ideal move. ]
;W[np]
C[When White answers with 2, ... ]
;B[qj]
C[... Black can invade with 3. ]
;W[pj];B[qk];W[pk];B[rl]
C[After 7, Black's stones on the right have a secure base. <= ]
)
(;B[qq]
C[Failure.  

Invading with 1 is not good. ]
;W[qp];B[pq];W[op];B[rp];W[ro];B[rq];W[qo];B[nq]
C[After Black secures his stones with 9, ... ]
;W[qg]
C[... White plays 10, attacking the two black stones at the top and strengthening her moyo on the right side. <= ]
)
)