Here's why:
* Prepositional phrases start with a preposition (like "on," "in," "to," "with," etc.) and are followed by a noun or pronoun (the object of the preposition).
* "To walk" is an infinitive, which is a verb form that usually begins with "to".
Example:
* Prepositional phrase: "to the store" (The preposition is "to," and the object is "store.")
* Infinitive: "to walk" (The verb is "walk," and it's in the infinitive form.)
Let me know if you'd like to explore other examples!