(No. 187: Nov. 22, 1999)
Elementary level: Answer
Cutting at Black 1 is the vital point.
If White 2, Black 3 kills White.
White cannot do anything further
because it is short of liberties.
If White 2 at 3, Black 2 kills White.
Elementary level: Wrong Answer
Black 1 allows White to get a Ko with 2.
Intermediate level: Answer
Black 1 and 3 are crucial to win the capturing race.
Intermediate level: Wrong Answer 1
Black 1 is wrong. After White 2 and 4,
Black has to create a Ko with 5 and 7.
Intermediate level: Wrong Answer 2
Black 3 is wrong. After White 4 and 6,
Black loses the capturing race.
Black can get a Ko by playing 5 at 6.