EVENT
BOARDSIZE 19
SETUP W C18 C17 D16 D14 R14 R11 Q4 Q6 R3 C6 D10 
SETUP B D17 E17 F16 F14 K16 P17 R16 Q2 O3 L3 D4 F4 
COM
Problem 107. White to play.  

The fuseki is almost over and the middle game is about to begin.
Where should White play ? 
ENDCOM
W 1 P15
MARK A@O17
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

White 1 is the vital point. When White plays here, she is expanding
her own moyo on the right and preventing Black from expanding
his moyo at the top. If Black doesn't answer White 1 and plays
elsewhere, White will attach at A.
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  VAR
  W 1 N5
  MARK A@E6
  COM
  Failure.

  Playing at 1 (or A) misses the point.
  ENDCOM
  B 2 P15
  COM
  Black will jump to 2 and a territorial moyo emerges at the top.
  If you compare this diagram with the Correct Answer, the difference
  should be obvious.
  <=
  ENDCOM
  ENDVAR
  VAR
  W 1 E6
  COM
  Failure.

  Also wrong.
  <=
  ENDCOM
  ENDVAR
B 2 O16
W 3 O15
B 4 N16
W 5 M14