Final answer:
The bold words from the student's question form a clause because it includes subjects and verbs and expresses a complete thought.
Step-by-step explanation:
The group of words in bold from the student's question represents a clause. A clause includes both a subject and a verb, and it can express a complete thought or idea when it's an independent clause, or be part of a larger sentence structure when it's a dependent/subordinate clause.
In the given sentence, 'lions are mostly nocturnal predators that hunt together, whereas cheetahs are diurnal predators that hunt alone' is a clause because it has subjects ('lions' and 'cheetahs') and verbs ('are', 'hunt') and conveys a complete thought.