Ko threat exercise 2
a Threatens to make Black's group live. White must respond at the other a. The value of this threat is nearly 30 points.
c Threatens to connect Black's dead group with his live corner by playing y. White must respond at y. c is generally better than y because after White responds at c, Black has added a stone to his dead group. c is an example of a ko threat that you wanted to play even without the ko. The value of this threat is almost 40 points.
In rare cases, y will be better than c, because it leaves a second threat at v. However, loss making threats like these are, as a rule, bad.
d Threatens to kill the white group. White must answer at z (the two points are miai, and Black could also have played z as a threat). The value of this threat is 30 points.
e White playing at e threatens to cut the two black groups apart. Each of them only has one eye, so they will die. Black must respond at f. White f is also a threat, but it loses points, while f takes a point of territory away from Black. The value of this threat is more than 50 points.
g These are small threats to reduce White's territory.