Traditionally, this line was given as the solution, on the point of symmetry leading to (indirect) ko.
Although the first diagram was long considered the solution, Go Seigen came up with this , the tesuji known as the ugly sagari. So really there is nothing black can do. The problem is now often given as a problem for white, how to respond to
Anon: What happens if B plays at
?
unkx80: I guess this. Note, has no time to play the throw-in at
, as
can capture by snapback at a.