Question

is the group of words in bold a phrase or a clause? built to honor all the gods, the pantheon is a monument that is an exceptional example of ancient roman architecture. phrase clause

Explanation:

A clause contains a subject and a predicate (a verb or verb phrase). The bolded group "that is an exceptional example of ancient Roman architecture" has a subject ("that", referring to "monument") and a predicate ("is an exceptional example..."). A phrase lacks a subject - predicate structure. So it's a clause.

Answer:

clause