(;
GM[1]
SZ[19]
AW[db][fc][hd][jd][lc][qf][pf][qi]
AB[cc][dd][cf][mb][nd][pd][qe]
TR[mb]
C[Problem 145. White to play.  

The marked black stone does not adequately protect the corner. White still has a way to invade. ]
;W[qc]
TE[2]
C[Correct Answer.  

First White invades at the 3-3 point, ... ]
(;B[re];W[ob]
C[... then slides to 3, threatening to link up to the white stones on the left. ]
;B[mc]
C[When Black defends at 4, ... ]
;W[rb]
C[... White lives with 5. <= ]
)
(;B[pc]
C[Variation.  

If Black 2 here, ... ]
;W[re]
C[... White hanes at 3. <= ]
)
(;B[qd];W[ob];B[mc];W[pc];B[oc];W[rb])
)