Kreuger flaps are
basically "crude" leading edge flaps. They do increase the camber and
therefore the CL max, but because of the sharp edge
they also induce flow separation at high angles of attack. For this reason they
are used close to the wing root to ensure root stall in aircraft that are prone
to tip stall.
Sophisticated leading edge flaps, maintain their nice smooth shape as they
change the camber. To do this they are more complex and heavier and a lot of
the new aircraft don't use them for that reason. Some of the older aircraft had
them on the mid sections of the wing leading edges.
Slats do not change the camber but they open a slot to accelerate the airflow
in the boundary layer to delay separation and therefore delay tip stalling, so
they are used on the outboard sections of the wing leading edges.
Many of the older Boeings used them in that order. Kreuger
flaps close to the root, then sophisticated leading
edge flaps on the mid sections and then slats on the outboard sections. The
modern Boeings still use Kreuger flaps close to the
root but then use slats for the rest of the wing as your picture shows.
Airbus because they use fly by wire to sort out the stability problems, use
full span slats, and don't worry about Kreuger flaps
or leading flaps.
Just for interest, Boeing still use triple slotted fowler flaps on the trailing
edge on most of their aircraft, but Airbus have opted for a single slotted
fowler flap.