Closing: amicable::argument: CONCISE
Closing means completion or settlement
Amicable means characterized by showing goodwill.
Argument means exchange of opposite views.
Concise means giving information in short.
An amicable settlement and a concise argument can go together.
B. downhearted
<span>depressed in spirits; disheartened; low-spirited:</span><span>The dejected expression on the face of the loser spoiled my <span>victory.</span></span>
She wasn't doing very well in her studies, so she tried to collaborate different studying techniques.
Appositive phrases are used to further describe the noun in front of them. Usually, they are set off from the rest of the sentence by commas on either side.
Having this in mind, the correct answer is B. a nocturnal hunter. It fits everything I wrote as an explanation here.