EVENT
BOARDSIZE 19
SETUP W D16 L17 D4 D5 D3 E3 E2 F4 J4 O5 P5 Q5 R4 
SETUP B Q17 R15 D2 C2 C3 C4 C6 F3 L3 N4 P3 P6 Q6 R6 
MARK \t@N4
COM
Problem 114. White to play.  

Black has reinforced his stones at the bottom with the marked
stone. How should White respond ? 
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W 1 Q3
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

This is a case where White must defend to ensure that her weak
stones don't come under attack. White 1 is the vital point for
White to make a base in the corner. Next, ...
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  VAR
  W 1 Q10
  COM
  Failure.

  White 1 is bad.
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  B 2 R2
  COM
  Black slides to 2, expanding his territory and robbing the four
  white stones of their base. White must escape, but with weak
  stones above and below, she is sure to fall behind as she tries
  to rescue them.
  <=
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  ENDVAR
B 2 Q2
MARK 1@Q3
COM
Besides securing a base for her stones, White 1 also attacks
the black stones. Black must defend with 2 ...
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W 3 R2
B 4 P2
COM
... and 4.
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W 5 S5
COM
White now secures the corner with 5, and ...
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B 6 Q10
COM
... Black will extend to 6, staking out a position on the right
side.
<=
ENDCOM