(No. 198: Feb. 7, 2000)
Elementary level: Answer
Black 1, sacrificing two stones, is the Tesuji to win.
After White 4, to the next diagram.
Elementary level: Answer (Continued)
Black wins the capturing race with 5 to 7.
If White 6 at 7, Black wins with 6.
Elementary level: Wrong Answer
Black 1 allows White to get a Ko with 2 to 4.
(An approach move Ko)
Intermediate level: Answer
The combination of Black's moves 1 and 3 is crucial.
If White 4, Black 5 kills White.
Intermediate level: Wrong Answer
Black 1 allows White to get a Ko with 2.