How does Shelley convey the idea that humans are

constantly moving and changing?

by personifying the moon

by comparing humans to

clouds
by personifying the night
by comparing humans to darkness

by comparing humans to  clouds

Explanation:

In the excerpt I posed to the comments, it is shown that Shelley conveyed the idea that humans were constantly mobile by comparing us to clouds.

Clouds are constantly moving across the surface of the earth as they are pushed by winds to other areas. In likening us to them therefore, Shelley is inferring that humans are constantly moving.

i have heard the mermaids singing, each to each.

i do not think they will sing to me