EVENT
BOARDSIZE 19
SETUP W F17 F16 K17 
SETUP B D16 E17 D14 N17 Q16 R10 
COM
Problem 121. White to play.  

How should White invade the black position on the right side
? 
ENDCOM
W 1 R16
MARK C@S15 B@R14 A@R17
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

This time, instead of the 3-3 point at A, White should invade
by attaching with 1. White could also invade at B or C.
<=
ENDCOM
  VAR
  W 1 R14
  USER
  CORRECT ANSWER
  ENDUSER
  COM
  Correct Answer.

  Also correct.
  <=
  ENDCOM
  ENDVAR
  VAR
  W 1 S15
  USER
  CORRECT ANSWER
  ENDUSER
  COM
  Correct Answer.

  Also correct.
  <=
  ENDCOM
  ENDVAR
B 2 R17
W 3 R15
B 4 Q17
W 5 R12
B 6 P10
W 7 P12
COM
The moves to 7 are joseki. White has succeeded in invading Black's
moyo.
<=
ENDCOM