Arby: This one was really hard. I had thought about B15 as a first move, but I couldn't figure out what the correct response would be after 2. C16 3. C15 4. A16.
After reviewing, I see the way forward for this line. Start with 5. A18, which forces 6. A19 capturing A18. Then after sealing in with 7. A15, the opponent is in atari and can only escape with 8. A18, but this leaves them in a lost capturing race.
kaspar: This doesn't seem like "easy life" anymore. It's ko. I'm guessing the original black move was A16 and white can live with: C19B14A18A15 (which also doesn't seem "easy") but it doesn't appear in the review so I'm just guessing.
Guennou: Can't White make a ko here ?
With B15C15C16A15 ? I see that there is no indication on that problem, but here it seems that White does not try the strongest defense.
It's a ko threat but ok.