what is an unmodified adverb? and what is a modified adverb? it is confusing me as to knowing when to use il est or c'est because I can't tell when it is modified or unmodified!!!

Hello! i'm marianne and i'm from montpellier, france. here is a picture of my family. in the photo, they are my grandparents, my uncles and aunts, and my parents. they are in the garden at my grandparents' house. this is my grandmother's birthday on november 8 and we are all at home for this occasion. my grandmother is seventy-nine! my grandfather is older. he is eighty years old! my uncles and aunts are very nice and interesting. they are with my parents and my grandparents in the picture. i take the picture and that's why i'm not in the picture. i'm happy with my grandparents because my cousins are there when we're here and we talk and play together. it's fun to be with the family. my family is very good and active. i love my family! how is your family? do you have cousins and grandparents? where are they?

Àqui est le livre? (moi)
le livre est à moi.
à qui est le drapeau? (adrien et andré)
c'est le drapeau de adrien et de andré.
à qui est l'ordinateur? (nous)
c'est notre ordinateur.
or
cet ordinateur est le notre.
à qui est la télé? (elle)
la télé est à elle.
à qui est le sac? (toi)
le sac est à toi.