Hi I'm confused on what is an stem extender and morphemes.

Underline any stem extenders in the word below.
Philosophy
Banana
Pheumectomy
Anthropology

How many morphemes do the following contain?
Sown 1
Airsickness 2?
Ohio 1
Algebra not sure.
expel 1?
Congenital 2?
Cognate 2?
herb 1
helicopter 3?
radii 1

Please help? thanks!