Final answer:
A confident.
The passage from 'I Hear America Singing' indicates that the singers feel confident, as they are described singing in a way that reflects pride and strength in their work.
Step-by-step explanation:
The passage from I Hear America Singing suggests that the singers feel A) confident. The poem by Walt Whitman describes various individuals engaging in their respective occupations and singing 'as it should be blithe and strong', which conveys a sense of pride and possession in their work. There's an overarching theme of joy and vigor associated with the American spirit through the act of singing. The poem does not indicate feelings of being mournful or uncertain, and while love might be present, it isn't the primary emotion depicted in relation to the singing.
Throughout the excerpt, Whitman's use of phrases like 'singing with open mouths their strong melodious songs' underlines the exuberance and confident spirit of the American people. The celebration of the individual and collective identity encapsulated in the act of singing showcases Whitman's optimistic view of democracy and the productive vitality of everyday Americans.