I'm pretty sure it is Theme.
Theme is the central topic of the text. passage, story, or anything else. So it may possibly also be the same for the underlying meaning and universal truth...but again, I am not sure.
Answer:
Clause
Explanation:
A phrase is like someone saying "It's raining cats and dogs!" that's a phrase. So that means it would be a clause.
Answer: the answer is D . Predicate nominative.
Explanation: I just did the test .
Subordinate clause
Hope it helps :)