Gokyo Shumyo, Section 1, Problem 17 / Solution

Main line  

White is tesuji.

Main line  

Later, if , then captures the stone and lives.

Wrong  

Leaving out the hane enables Black to play hane himself. The most White can get out of it is to starting a (terribly disadvantageous) ko at a.

Wrong (ii)  

The throw-in at and the atari at will throw the entire black group into a ko.

Wrong (ii) (cont)  

If White connects the ko at , the atari at blows the eyeshape away. If White doesn't, a black capture at continues the ko.

Wrong  

White here doesn't threaten anything, giving Black the time to make an eye false at .