Kyu Exercise 74 / Solution

Solution  

After , Black cannot play at a. But what about at b?

Then there are two reasonable continuations: a or c. It should be noted however, that White cannot kill the Black group:

White having fantasies  

Black has no problem to force life for his four stones.

In reality White or Black would divert from this path at some point. Also there are ladders involved and the area further down the side (There already is one row added to this diagram.).