Gokyo Shumyo, Section 2, Problem 2 / Solution

Main line  

kills the group without ko. This line works in the corrected version too.

Variation 1: here also kills  

a and b become miai for the kill. This is inferior to the main line because white has more ko threats.

Variation 2: captures  

After white is left with the bulky 5 shape.

Alternatives

Attack from the right  

However Black has three more moves to kill: a to c.

shortage of liberties  

For example, this line kills because White can't connect at a.