TsumegoFromGames134/Attempts

Ko, black takes first  

Herman: Correct! Also, after white retakes, the move at a is an internal ko threat, requiring b from white to continue the ko. But since this is a flower viewing ko for white, black should probably sacrifice those 4 stones...

No internal threat  

Dieter: I think that White should exchange - first to deny Black his internal threat.

No Resistance  

Black cannot resist.