(;
GM[1]
SZ[19]
AW[dd][cj][ek][fj][fl][fm][cl][cn][dn][dp][eq][lj][kk][kl][jl][im][in][hn][ip][nc][pb][qc]
AB[fq][fp][el][em][en][fn][gn][gm][hm][hl][il][ij][jk][kj][ki][mp][pq][pk][pd][pf][lc][le]
TR[ip][in][hn][im][jl][kl][kk][lj]
C[Problem 78. Black to play.  

How should Black attack the marked white stones ? ]
(;B[kn]
TE[2]
C[Correct Answer.  

Black should peep at 1 to destroy White's eye shape. ]
;W[km];B[mn];W[ml];B[li];W[mj];B[nk]
C[After Black 7, White's stones have barely one eye, while Black is threatening to make a moyo in the lower right. <= ]
)
(;B[lk]
C[Failure.  

Cutting with 1 ... ]
;W[kn]
C[... lets White make an eye with 2. ]
;B[mk];W[qo]
C[Since her stones are now relatively secure, she can invade Black's sphere of influence in the lower right with 4. <= ]
)
)