Which of the following would a romanticism author most likely write about?
a.) photosynthesis.
b.) land reform policies.
c.) the beauty of a weeping willow.
d.) political reasons for revolution movements.

 Romanticism author usually are famous for the picture they sketch with their words about nature and beauty
so He would like to write about the 
the beauty of a weeping willow
so i conclude option C is correct
hope it helps