What are the principal ideas of romanticism? how are these reflected in art and literature?

Reason:

the rise of nation-states as defining social and geographic entities
increasing geographic and social mobility, with more people moving to cities & the growth of a literate middle class,
new technologies dependent on power from fossil fuels (trains, steamships, industrial printing)
longer life-spans and rising standards of living enable ideas or values including individualism, imagination. idealization of childhood, families, love, nature, and the past.

The answer is a : varying the size of objects or subjects, so that some are smaller than others and the illusion of depth is created.hope this : )

You look through the lens