(;
GM[1]
SZ[19]
AW[dd][cq][dp][dn]
AB[pd][pp][dr][fq]
TR[cq]
C[Problem 49. Black to play.  

What should Black do after White plays the marked stone ? ]
(;B[iq]
TR[dr][cq]

TE[2]
C[Correct Answer.  

After exchanging the marked stones, Black must extend to 1. ]
;W[dj]
C[White 2 would then be the usual move in this position and ... ]
;B[pj]
C[... Black would make a sanren-sei on the right side with 3. <= ]
)
(;B[pj]
C[Failure.  

Rushing to make a sanren-sei with 1 is bad. ]
;W[hq]
C[White 2 ... ]
;B[fo];W[ho]
C[... and 4 severely attack the black stones, robbing them of a base. ]
;B[fm]
C[After Black 5, ... ]
;W[dk]
C[... White takes profit on the left side with 6. <= ]
)
)