Answer:
C.
Step-by-step explanation:
Allusion is a literary device that is used to give indirect and short credential to the things, places, person, idea, etc of past.
"Grass" is a poem penned by Carl Sandburg. The poem is written in the memory of those who lost their lives fighting for the nation. The poet urge the readers not to forget their sacrifices. The poem also talks about how nature works to cover or erase the wounds of the wars.
In the given passage, the poet has used allusion by referring to the war of Waterloo. The nature is playing an important role in the passage, by covering tthe great losses, even of the battles as Waterloo.
So, the correct answer is option C.