(No. 177: Sep. 13, 1999)
Elementary level: Answer
Black 1 is the vital point. Then Black 3 kills White.
Elementary level: Wrong Answer
Black 1 lets White get a Ko with 2.
Intermediate level: Answer
Black 1 is crucial. Black lives
by getting a Seki with the moves to 7.
Intermediate level: Wrong Answer
Black 1 is wrong. After White 2 and 4, Black is dead.