prep. except, besides, but - "Save"

prep. except; besides; but

(a) behind
(b) beyond
© concerning
(d) save

I am unable to understand why “save” is the correct anoswer for the above prep test

It is correct because it is the only one whose definition accords with “except,” “besides” and “but.” It also means “except.”

“Behind,” of course, refers to physical position. You know it can’t be right.
“Beyond” has several meanings, none of which is “except.”
“Concerning” means “about.”