This problem assumes that the reader knows how a ko fight works.
This shape looks like the twisted four, but it is at the corner. We note that when the group has only one outside liberty at , Black can turn the status of this group into a ko. This is similar to bent four in the corner.
If here, leaves the White group in a bent three.
This discussion is at a slightly higher level than the intended level of the problem.
Whether this is a picnic ko is not clear. If White wins, he lives; if Black wins he dies. Hence, we cannot say that this ko is lopsided. Perhaps White invaded Black's corner and managed to make ko. That kind of thing is not unusual. It is a mistake to think of something as your territory unless your opponent cannot invade to any effect.
This lives too.
What about White trying to escape? If White answers with , Black still needs to play , so White can connect at .
Coconuts: Even if black disregards the ko "threat" here and lets white connect, white is not away yet. B at a or b pretty effectively pins the white group down, so unless white has a strong position on the top side of the board, she is still in a lot of trouble.
Previous comment was not true. If black tries to pin white, she can play oshitsubushi at circle point and live. Black cannot disregard white's move on previous diagram.
The above comment looks incorrect to me. In the "Not out of the woods" diagram above, is the threat to escape, and then occupies the corner spot allowing the escape. Since the corner is already a bent three, it's just a single eye.
My mistake, I thought that B plays tenuki with in previous comment.
If black plays b, white can play at a, and white would have two eyes. If black plays a, white can play at c, and white can escape depending on what else goes on on the board.--Daniel Wang
Sorry Daniel, but if black plays b and white plays a then the ko may continue, provided of course that black has sufficient ko threats.--Rick Lush
Actually, this also shows that white cannot escape simply because black plays at "b." Escaping refers to moving out of danger areas. This white isn't going anywhere.--ProtoDeuteric