The best word to complete the sentence is "defiant." The sentence would read: "Annika tried to get her little brother to bed, but he was defiant."
Here's a brief explanation of the options:
- "defiance" (noun) - the act of resisting or opposing.
- "defiant" (adjective) - showing resistance or disobedience.
- "defiantly" (adverb) - in a manner that shows resistance or disobedience.
- "defy" (verb) - to openly resist or refuse to obey.
Since the blank in the sentence requires an adjective to describe "little brother," "defiant" is the correct choice.