Beginner Exercise 16 / Solution

Failure ( at )  

Automatic atari is a decisive mistake - after , the snapback will destroy Black's chance to make two eyes and the whole group dies.

Solution  

The enemy's key point is yours - after , White can't play at a immediately. After White captures at b, Black connects at a and secures two eyes.

Black dies outright  

If Black plays atari at , White captures three stones with , which also destroys any chance of a second eye.