EVENT
BOARDSIZE 19
SETUP W E16 G14 L16 O16 O17 Q4 Q5 Q3 P3 P2 L4 C3 C2 D4 D5 D10 
SETUP B D17 C16 D14 J14 J16 P17 Q16 Q14 Q2 R2 R3 R6 R4 O3 D3 E3 
MARK \t@E16 \t@G14
COM
Problem 89. Black to play.  

How should Black attack the two marked stones ? 
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B 1 H12
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Attacking with the knight's move of Black 1 is the correct direction.
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  VAR
  B 1 E11
  COM
  Failure.

  Black 1 is not a good move because it doesn't have a good follow-up.
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  W 2 H13
  COM
  After White escapes into the center, ...
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  B 3 E10
  COM
  ... Black exchanges 3 ...
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  W 4 D8
  COM
  ... for 4, ...
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  B 5 E9
  COM
  ... then extends to 5.
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  W 6 J13
  MARK \t@J16 \t@J14
  COM
  White extends to 6 and the two marked stones are under siege.
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  B 7 D9
  MARK A@K14
  COM
  If Black tries to press his advantage on the left side, White
  can take control of the top with A.
  <=
  ENDCOM
  ENDVAR
W 2 G12
B 3 G11
W 4 F12
B 5 H11
W 6 D12
COM
After White 6, 
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B 7 J17
MARK A@F15
COM
... Black makes an iron pillar at 7, aiming at A as well as the
three white stones on the right.
<=
ENDCOM