Beginner Exercise 127 / Solution

Black lives  

separates the small eyespace into two eyes, a and b.

Inside attack  

has to be answered by . at a lives too but with less points.

Mistake  

here is a mistake - turn it into a ko. If at a, White connects at and kills.

Failure 1 ( at )  

here dies - and make the second eye false.

Failure 2  

maximizes the eyespace, but the bulky five is obvious. After White takes the vital point with , a and b are miai to kill.