Which sentence contains an allusion

i think the answer is d.

the sample answer on e2020

conflicting values are demonstrated between two different groups in animal farm. first, the farm animals value hard work. this is shown by them working late and working long hours at the request of the pigs. napoleon and the pigs, however, sleep late daily. furthermore, the animals value equality. this differs from the value of napoleon and the other pigs. instead of equality, they value only gaining power and maintaining their own privilege, which is demonstrated by their taking extra milk and sleeping in beds.

to and without are prepositions, so a, b, and d are prepositional phrases. the adverb phrase is c, about the surprise.

explanation:

the underlined phrase is an example of : understatment