Answer: The words in this sentence that are prepositions are "on" and "for".
Explanation: A preposition is a word that precedes a noun or a pronoun and it is used to link that noun or pronoun to another word in the sentence. Moreover, they conform a closed class because it is made up of a finite set of words, that is to say new words are generally never added. "On" and "for", which are included in the sentence provided, are part of this set. In contrast, "early" and "now" are adverbs, "this" and "the" are determiners, "morning" is a noun and "our" is a pronoun.