Question

look at this thesaurus entry:
enliven
part of speech: verb
definition: to fill with life
synonyms: animate, brighten, cheer, energize, restore
which might you try to enliven?
someones mood
a car that is breaking down

Explanation:

The word "enliven" means to fill with life. A person's mood can be made more lively (e.g., cheered, energized), while a breaking - down car is a mechanical object and can't be "filled with life" in the same sense as a mood.

Answer:

someone's mood