Final answer:
The bolded word group, 'of leftover debris—ice, dust, rock' in the sentence is a phrase.
Step-by-step explanation:
The bolded word group, 'of leftover debris—ice, dust, rock' in the sentence, 'The solid portion of a comet comprises leftover debris—ice, dust, rock—that originated in the outer regions of the solar system,' is a phrase. It functions as a noun phrase and provides additional information about the solid portion of a comet.
The bolded word group in the statement "The solid portion of a comet comprises leftover debris—ice, dust, rock—that originated in the outer regions of the solar system." is a phrase. A phrase is a group of words that stand together as a single unit, typically functioning as a part of speech.
It is not a complete sentence as it does not have a subject and a verb. In contrast, a clause contains both a subject and a verb, and it can stand alone as a sentence or be a part of a more complex sentence.