Here's why:
* Prepositional phrases are groups of words that begin with a preposition (like "in") and end with a noun or pronoun (like "exam").
* Prepositional phrases function as adverbs or adjectives within a sentence.
For example:
* "I am in exam mode." (The phrase modifies the verb "am" and functions as an adverb.)
* "The questions in exam were challenging." (The phrase modifies the noun "questions" and functions as an adjective.)