Read this excerpt from Henry David Thoreau's "Resistance to Civil Government"

Unjust laws exist: shall we be content to obey them, or shall we endeavor to amend them, and obey them until we have succeeded, or shall we transgress them at once?

Which of these rhetorical devices does Thoreau most clearly use here?
A Ethos
B Metaphor
C Alliteration
D Rhetorical Question