 What is the simplest description of what Miss Meuhl and Retief are in the minds of the Groacian race? Why is this significant to the story?
"Miss Meuhl," he said, "in the past couple of weeks I've sat through six light-concerts, four attempts at chamber music, and god knows how many assorted folk-art festivals. I've been tied up every off-duty hour since I got here—" "You can't offend the Groaci," Miss Meuhl said sharply. "You've been here on Groac for four years, Miss Meuhl. Retief backed, rounded a corner into a narrow alley-like passage, deserted, silent ... except for the following Groacian. Miss Meuhl said, eyeing Retief over her lenses. Two Groaci wearing heavy eye-shields and elaborate crest ornaments indicative of rank rose as Retief entered the room.
 They are aliens. This is significant because Groacians see humans as alien to their planet, which helps the reader understand how prejudice develops on Groac.
 They are illegal space travelers. This is significant because the crimes of explorers like them are what prompted the Groaci to hide the first human cruiser that arrived.  They are colonialists. This is significant because it is Miss Meuhl and Retief’s desire to colonize Groac that fuels the Groacian hatred of foreigners.  They are slaves. This is significant because it helps the reader understand that Retief is lashing out as a result of being oppressed for so long.  They are aliens. This is significant because Groacians see humans as alien to their planet, which helps the reader understand how prejudice develops on Groac.