EVENT
BOARDSIZE 19
SETUP W K16 O16 Q17 P17 
SETUP B D16 H17 M16 R17 Q16 Q14 
MARK \t@M16 3@P17 1@Q17 2@R17
COM
Problem 12. Black to play.  

In response to Black's invasion with the marked stone, White
plays 1 and 3. How should Black respond ? 
ENDCOM
B 1 R18
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black should simply descend to 1, taking the corner. White still
cannot link up her stones.
<=
ENDCOM
  VAR
  B 1 M14
  COM
  Failure.

  Black 1 is possible, but ...
  ENDCOM
  W 2 R18
  COM
  ... after White 2, Black suffers a loss in the corner.
  <=
  ENDCOM
  ENDVAR