EVENT
BOARDSIZE 19
SETUP W D16 R10 D3 
SETUP B Q4 R16 P17 
MARK \t@R10
COM
Problem 56. Black to play.  

How should Black respond after White plays her marked stone ?
ENDCOM
B 1 D5
MARK A@C5
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

It is best for Black to make an approach move at 1 or A to prevent
White from making a corner enclosure.
ENDCOM
  VAR
  B 1 C5
  USER
  CORRECT ANSWER
  ENDUSER
  COM
  Correct Answer.

  Also correct.
  <=
  ENDCOM
  ENDVAR
W 2 C5
COM
If White attaches at 2, ...
ENDCOM
B 3 C6
W 4 C4
B 5 D7
W 6 F3
B 7 C11
COM
... the joseki to 7 will follow.
ENDCOM
W 8 C13
COM
Attacking Black's formation on the left with White 8 is now the
most reasonable move.
<=
ENDCOM