Read this dictionary entry for the word domain. domain (doh-mayn) n.

complete and absolute ownership of land
a region distinctively marked by some physical feature
a sphere of knowledge, influence, or activity
the highest taxonomic category in biological classification ranking above the kingdom
a subdivision of the Internet consisting of sites with a common purpose
Which sentence uses the word domain as it is described in the third definition?

The domain of the deadly blue-ringed octopus lies in the Pacific Ocean.
In biology, there are three domains: archaea, bacteria, and eukarya.
The king ruled that the land between the two rivers was under his domain.
In the domain of literature, William Shakespeare is a prominent figure.