Here's why:
* Participle: "Quivering" is the present participle of the verb "to quiver."
* Phrase: It functions as a phrase, modifying the noun "voice."
* Participial Phrase: A participial phrase is a group of words that includes a participle and its modifiers (if any) that act as an adjective.
Example:
"The voice quivering with fear, she whispered, "I saw him."
In this example, the participial phrase "voice quivering" acts as an adjective modifying the noun "voice," describing its state.