(No. 240: Nov. 27, 2000)
Elementary level: Answer
Black 1 is the vital point.
The result is a Seki with the moves to White 6.
Elementary level: Wrong Answer
Black 1 allows White the vital point 2
and loses the capturing race.
Intermediate level: Answer
Black 1, 3 to 5 is crucial.
After White 6, Black 7 gets a Ko.
If White 6 at 7, Black 6 wins the capturing race,
utilizing White's shortage of liberties.
Intermediate level: Wrong Answer
Black 1 first and then 3 fails.
After White 4, there is nothing that Black can do.