Step-by-step explanation:
In the sentence "She seems to know this place," the phrase "to know" is (C) an Infinitive.
Infinitives are verb forms that are typically preceded by the particle "to." In this case, "to know" functions as the complement of the verb "seems" and expresses the action or state of knowing this place. It functions as a noun in this sentence, serving as the direct object of the verb "seems."