(;
GM[1]
SZ[19]
AW[ec][ic][ql][po][qp][ko][kp][kq][gq]
AB[dp][pd][cd][de][qr][oq][np][lp][iq][io]
LB[gq:1]
C[Problem 154. Black to play.  

White attacks the two black stones by invading at 1. How should Black respond ? ]
(;B[fp]
TE[2]
C[Correct Answer.  

Black should treat the two black stones at the bottom lightly and jump to 1. ]
;W[ir]
C[White can save the invading stone by attaching at 2, but this is quite small. Next, ... ]
;B[cj]
C[... Black takes the key point of 3 and all of his stones on the left side are working efficiently. <= ]
)
(;B[hp]
C[Failure.  

Preventing White from linking up by playing 1 is not good. ]
;W[fo]
C[White jumps to 2 and the three black stones become heavy. There is no comparison between this result and the one in the Correct Answer. <= ]
)
)