EVENT
BOARDSIZE 19
SETUP W D17 D4 
SETUP B Q4 Q16 
COM
Problem 1. Black to play.  

Black has made a niren-sei formation on the right. If Black wants
to play on the left side, which approach move should he make
? 
ENDCOM
B 1 D15
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black usually plays the one-space high approach move at 1. This
move is preferred because White does not have a good pincer against
Black 1 in relation to his marked stone in the lower left.
<=
ENDCOM
  VAR
  B 1 C15
  COM
  The low approach.

  If Black plays a low approach with 1, ...
  ENDCOM
  W 2 D12
  COM
  ... White pincers at 2.
  ENDCOM
    VAR
    W 2 C11
    MARK \t@D4
    COM
    The three-space pincer.

    The three-space pincer of White 2 is a good extension from White's
    marked stone below.
    ENDCOM
    B 3 D16
    W 4 E17
    B 5 C17
    W 6 C18
    B 7 B17
    COM
    Black would most likely settle his stones with the sequence to
    7, but ...
    ENDCOM
    W 8 H17
    COM
    ... then White 8 would reduce the influence of Black's star-point
    stones on the right.
    <=
    ENDCOM
    ENDVAR
  B 3 D14
  W 4 F16
  B 5 B17
  W 6 K17
  COM
  If the joseki to 6 follows, the white stone at 6 reduces the
  influence of Black's star-point stones on the right.
  <=
  ENDCOM
  ENDVAR