EVENT
BOARDSIZE 19
SETUP W C18 D17 E18 F16 L17 P17 D11 C10 C6 C5 D4 C3 C2 S4 S3 R3 Q3 O3 R6 
SETUP B R16 Q15 C17 C16 D15 C12 C8 E8 B6 D2 F3 J3 P4 Q4 R4 R5 S5 Q8 Q11 
MARK \t@D11 \t@C10
COM
Problem 99. Black to play.  

How should Black attack the two marked white stones ? 
ENDCOM
B 1 F10
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black should drive White towards the top with the knight's move
of 1.
ENDCOM
  VAR
  B 1 F14
  COM
  Failure.

  Black 1 certainly keeps the white stones from linking up to their
  allies at the top, but ...
  ENDCOM
  W 2 D12
  B 3 C13
  W 4 G11
  B 5 H9
  W 6 J11
  B 7 K9
  W 8 L11
  MARK C@F12 B@G13 A@E14
  COM
  ... White easily escapes into the center with the sequence to
  8. Black's prospects for making a moyo at the bottom are no longer
  realistic because Black must defend against White A. If Black
  B, White C keeps the threat A viable.
  <=
  ENDCOM
  ENDVAR
W 2 D12
COM
After exchanging 2 ...
ENDCOM
B 3 C13
COM
... for 3, ...
ENDCOM
W 4 F12
COM
... White jumps to 4.
ENDCOM
B 5 H11
COM
Black keeps up the attack with 5, and, ...
ENDCOM
W 6 F14
COM
... after White 6, ...
ENDCOM
B 7 F6
MARK B@K12 A@H13
COM
... jumps to 7 to make a moyo in the lower left. If White A,
Black will jump to B.
<=
ENDCOM