BeginnerExercise251/Solution

The only move.  

P7A77: It seems there is death in the hane. This makes a and b miai. Other moves may be sente for black, but result in life for white.

Failure: Not even ko.  

here is a mistake: now white is alive.

P7A77: Black can't connect. If black connects with , the same makes miai of the diagram's and the marked space.

xela: Well, black can connect. It doesn't work, but neither does in your diagram. I'll add another couple of diagrams to show how the connection fails.

After in the previous diagram  

White can play either a or b for a second eye.

Nope.  

P7A77: Every wrong answer has White playing , which indicates that's the move for Black.