The correct option is A flag - Concrete Noun; epitome, unity - Abstract Nouns
refer to things that cannot be perceived through any of our senses
(touch, see, taste, smell, hear). They are emotions or states of being.
For example, 'happiness', intelligence', etc.
Concrete nouns are the opposite of abstract: they can be perceived through the senses.
Option A: A 'flag' is a piece of cloth that represents a country or an institution. It is seen and touched, hence it's a concrete noun.
'Epitome' means an example that is set by someone. An epitome cannot be seen, or perceived by our other senses. Hence it's abstract.
'Unity' refers to the state of being united. It's an abstract noun.
Since this option has correctly categorized the nouns, this is the right answer.
Options B, C and D:
A 'flag' is not a state or an idea that it can be abstract.
'Unity' cannot be perceived through any of our senses, hence it's not concrete.
So, these options are incorrect.