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

Select the option that can be used as a one-word substitute for the given group of words.
The act of expressing profound and often bitter grief or lamentation, especially in a public or formal setting, for a loss that is perceived to be irrecoverable

Select the most appropriate one word for the expression given below.

The branch of philosophy concerned with the theory of knowledge

Select the most appropriate one word for the expression given below.

A politically organised community or major territorial unit ruled by a monarch