EVENT
BOARDSIZE 19
SETUP W D16 K16 O17 D4 R3 R4 Q5 R7 
SETUP B Q16 Q14 Q9 Q3 O4 K4 R2 S2 
MARK 5@R7 4@S2 3@R4 2@R2 1@R3
COM
Problem 15. Black to play.  

White has staked out a narrow position with the sequence to White
5, a standard joseki in the Chinese opening. What should Black
do next ? 
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B 1 S8
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.  

Black should attack the white stones with 1.  
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  VAR
  B 1 F3
  COM
  Failure.  

  With respect to the black stones at the bottom, Black 1 is an
  excellent move, but ...  
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  W 2 S9
  MARK B@M3 A@P3
  COM
  ... White will slide to 2, intruding into Black's territory on
  the upper right while securing a base for her stones. Now that
  her stones are safe, White can aim at Black's territory at the
  bottom by attaching at A or invading at B.  <= 
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  ENDVAR
  VAR
  B 1 R8
  COM
  Unsatisfactory.

  The diagonal attachment of Black 1 is inferior to the Correct
  Answer.
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  W 2 Q7
  B 3 O9
  W 4 O7
  MARK A@R10
  COM
  Not only are White's stones secure, but White can also aim at
  the invasion at A.
  <=
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  ENDVAR
W 2 P7
COM
If White jumps to 2, ...  
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B 3 O9
COM
... Black keeps up the pressure with 3, attacking White while
building influence towards the top. White's stones are still
insecure.  <= 
ENDCOM