EVENT
BOARDSIZE 19
SETUP W C3 R4 
SETUP B D16 R16 
MARK A@P17 B@R10 C@P3
COM
Problem 112. Black to play.  

There are many ways for Black to play in this fuseki, but, if
you were going to play on the right side, which one of the three
moves from A to C would you choose ? 
ENDCOM
B 1 P17
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Making a corner enclosure with 1 is the simplest way for Black
to keep his first-move advantage.
ENDCOM
  VAR
  B 1 P3
  COM
  Failure.

  If Black 1 here, ...
  ENDCOM
  W 2 P17
  COM
  ... White can equalise by approaching at 2.
  <=
  ENDCOM
  ENDVAR
W 2 R11
COM
White must extend to 2 to stop Black from making a moyo on the
right, but ...
ENDCOM
  VAR
  W 2 P3
  MARK 1@P17
  COM
Reference Diagram.

  If White responds to Black 1 by making a corner enclosure of
  her own, ...
  ENDCOM
  B 3 R10
  COM
  ... Black will make an ideal extension with 3, taking control
  of the right side.
  <=
  ENDCOM
  ENDVAR
B 3 P4
W 4 P3
B 5 O3
W 6 Q3
B 7 O4
W 8 Q5
B 9 K4
COM
... Black takes up a position at the bottom with the joseki to
9.
<=
ENDCOM