Pay-___-click (advertising model) (3)
I believe the answer is:
per
(Other definitions for per that I've seen before include "For each or every" , "According to" , "Preposition meaning for each" , "Preposition indicating by means of" .)
I believe the answer is:
per
(Other definitions for per that I've seen before include "For each or every" , "According to" , "Preposition meaning for each" , "Preposition indicating by means of" .)