(;
GM[1]
SZ[19]
AW[lc][qf][pj][qn][cf][bd][ci]
AB[cc][dd][fd][jd][nd][pd][pp][np][jp][dp]
LB[lc:1]
C[Problem 56. Black to play.  

The deep invasion of 1 is another move White has in her arsenal. How does  Black reply in this case ? ]
(;B[ld]
TE[2]
C[Correct Answer.  

Attaching with Black 1 is the strongest move. White is now forced to make life on the side. ]
;W[mc];B[md];W[kc];B[jc]
(;W[pb];B[kd];W[nc]
C[The moves to 8 are joseki. Black gets territory on the left and thickness in the center. <= ]
)
(;W[kd]
C[White could push through with 6 ... ]
;B[ke];W[jb];B[ib];W[ka];B[je];W[ob]
C[... and live with the moves to 12. This is also joseki. <= ]
))
(;B[nc]
C[Failure.  

Defending with Black 1 is bad. When White makes a deep invasion, your first instinct should be to confine her to the side. ]
(;W[le]
C[<= ]
)
(;B[mc]
LB[kc:A]
C[Failure.  

Attaching with 1 (or A) is even worse. ]
;W[ld];B[nf];W[lf]
LB[oc:A]
C[White is out into the center and still threatens a move at A. <= ]
)
(;B[jc]
TE[2]
C[Correct Answer.  

If you are going to defend, Black 1 is the only way. ]
;W[le]
C[After White 2, ... ]
;B[og]
C[... Black jumps to 3, attacking White on both the right and the left. <= ]
)
(;W[jc]
LB[le:@]
C[Instead of @, White could attach at 2. ]
;B[ic]
C[Black plays 3 and ... ]
;W[id]
C[... White cuts at 4. <= ]
))
)