Tapir: After i see ko after with all black answers i can imagine (most notably a, b, c)
unkx80: You sure Black b results in a ko?
No, actually. Btw, are you seeing the answers or do you have to study the problems for some minutes to get it?
unkx80: For this problem the "answer" came to me almost immediately when I saw your attempt, as if it is intuition. But most problems, I need some minutes to solve it, and might not get them totally right.
Tapir: Like, if black at b prevents the ko, so white must play there first... ? Is a double ko (it is, isn't it) with two local threats for white a valid solution?