"Silver trucks heavy with oil or paper–
bricks or milk, teeming over highways alongside us,
on our way to clean tables, read ledgers, or save lives–
to teach geometry, or ring-up groceries as my mother did
for twenty years, so I could write this poem for all of us today. "

The last lines of the second stanza creates a sense of unity by referencing

A the shared experience of listening to loud noises
B the shared experience of the American workforce
C the shared experience of teaching and learning
D the shared need to move and travel

Based on the stanza (which I believe is the entire paragraph displayed above the question), we can immediately disqualify A. as a choice, as there is not a lot of references to "listening to loud noises". We can also eliminate D. as there is no mention of a shared need to move and travel. This leaves us with two options: B and C. From here, I think both could work, but what led me to believe that B is the correct option is because there is always some sort of work that is being talked about in the paragraph. "clean tables, read ledgers, or save lives-to teach geometry, or ring up groceries as my mother did". I believe the line I just quoted really demonstrates how B is the right answer. Please let me know if I misunderstood and I hope I helped!