What is the function of the noun clause in this sentence?

The street musicians sang to whomever passed them.

subject

appositive

object of a preposition

direct object

Object of a preposition

Object of a preposition

Explanation:

The noun clause of the sentence is "whomever passed them" because it is a group of words having a subject (whomever) and a verb (passed), acting as a noun and which can be referred to with pronouns like "it" and "that." As a noun, this clause functions as the object of the preposition "to" because it is placed next to this preposition and completes its meaning (the proposition would not make sense without this clause).