When using prepositions of reference and Manner I'm confused on how to explain when to use the "in" and "on" in a sentence like with in: MANNER: The child ran down the steps in tears. REFERENCE: In my opinion we need a referendum. They are happy in their marriage. How do i explain to someone why on wouldn't be used in any above or why in is used in those sentences? or with on: REFERENCE: He asked my opinion on the matter. CONDITION: We’ll hire him on your recommendation.