Question

is the group of words in bold a phrase or a clause?
the hippopotamus, an extremely dangerous and highly aggressive animal, will attack if it is provoked or feels threatened.
phrase clause

Explanation:

A phrase is a group of words without a subject - verb pair, while a clause has both a subject and a verb. The bolded group "an extremely dangerous and highly aggressive animal" has no verb, so it is a phrase.

Answer:

phrase