Select the most appropriate 'one word' for the expressions given below.
Done, occurring, or active at night.

Correct option is A

The correct one-word for the given group of words is (a) Nocturnal.
Nocturnal means active, occurring, or done at night. It is mostly used to describe animals or habits. (रात्रिचर)
Example: Owls and bats are nocturnal creatures.
Meanings of the given other options:
· (b) Cothurn: A type of ancient Greek shoe or boot (प्राचीन ग्रीक जूता)
· (c) Adjournal: A postponement or suspension of proceedings (स्थगन)
· (d) Diuturnal: Lasting for a long time, enduring (दीर्घकालीन)