Black wins with , x, or y.
is best, with two advantages over the rest:
1) White's play at a is not sente, and
2) the marked stones have more liberties in some continuations.
If Black chooses x in the above diagram, forces
- it tactically affects the top side. For example, Black can't catch
because of
! - Black can't play at a.
If Black chooses y in the first diagram, the same tactics occurs with more serious effect because White's corner has two liberties. Later, White a will be sente - White b next makes seki.