(;
GM[1]
SZ[19]
AW[jd][lc][nd][oc][pc]
AB[dd][hc][ld][pd][qc][qd][pf]
TR[pc][oc]
C[Problem 15. Black to play.  

Having played the marked stones, White returns to attach at 1. How should Black reply ? ]
(;B[kc]
TE[2]
C[Correct Answer.  

Black 1 is the vital point. ]
;W[kd];B[mc];W[lb];B[md];W[mb];B[jc]
C[The exchange continues up to 7 and the white stones have become separated. Moreover, the white group at the top is still not completely alive. <= ]
)
(;B[mc]
C[Unsatisfactory.  

If Black hanes on the other side with 1, ... ]
;W[md];B[kc];W[lb];B[kd];W[kb]
C[... White can make life at the top up to 6 ... ]
;B[jc]
C[... in sente. <= ]
)
)