EVENT
BOARDSIZE 19
SETUP W Q17 N17 Q12 R8 Q4 
SETUP B C15 D4 O15 R15 R6 
MARK A@D17 B@P6 C@R3 \t@R8
COM
Problem 117. Black to play.  

White has just pincered with the marked stone. Should Black answer
it by jumping to B, invading at C or making a corner enclosure
with A ? 
ENDCOM
B 1 P6
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Jumping to 1 is the ideal move.
ENDCOM
  VAR
  B 1 R3
  COM
  Failure.

  Invading with 1 is not good.
  ENDCOM
  W 2 R4
  B 3 Q3
  W 4 P4
  B 5 S4
  W 6 S5
  B 7 S3
  W 8 R5
  B 9 O3
  COM
  After Black secures his stones with 9, ...
  ENDCOM
  W 10 R13
  COM
  ... White plays 10, attacking the two black stones at the top
  and strengthening her moyo on the right side.
  <=
  ENDCOM
  ENDVAR
W 2 O4
COM
When White answers with 2, ...
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B 3 R10
COM
... Black can invade with 3.
ENDCOM
W 4 Q10
B 5 R9
W 6 Q9
B 7 S8
COM
After 7, Black's stones on the right have a secure base.
<=
ENDCOM