EVENT
BOARDSIZE 19
SETUP W D17 F17 C16 C15 C8 D4 
SETUP B C14 D14 D15 D10 Q16 Q4 
MARK 1@D10 2@C8
COM
Problem 9. Black to play.  

In response to Black 1, White has extended to 2, attacking the
weak underbelly of Black's position. With the whole board in
mind, where should Black play his next move ? 
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B 1 Q10
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Instead of defending his stones on the left side, Black makes
the sanren-sei formation on the right side with 1.
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  VAR
  B 1 C10
  COM
  Failure.

  Black is thinking on a small scale if he defends at 1.
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  W 2 R10
  COM
  White will immediately take the big point on the right side with
  2.
  <=
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  ENDVAR
W 2 C12
COM
Black now welcomes the invasion of White 2 ...
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B 3 D12
W 4 C11
B 5 D11
W 6 C10
B 7 D9
COM
... because the thickness he builds with the sequence to 7 words
very well with the influence of his three stones on the right.
<=
ENDCOM