Gokyo Shumyo, Section 1, Problem 25 / Solution

White lives  

makes miai of a and b. It is the vital point.

Main line  

makes miai of a and b.

Note  

The exchange and doesn't affect the solution.

Wrong 1  

makes an incomplete shape and is just the point to spoil it. After , a and b are miai.

Wrong 2  

here is a weaker vital point. is more vital, moreover because threatens to capture two stones and take away all the eye space.

Wrong 3  

Maybe an example of how to die in gote. White 1 definitely is the move to play if you want to ruin your own shape. This is a way of suicide which is not forbidden by the rules.

Wrong 3 (continuation)  

After plays tenuki, White still can't live.