Step 1: Identify the source of the quote.
The line "O how feeble is man’s power" is from Walt Whitman’s *Song of Myself*. This poem reflects Whitman’s philosophy of individualism and the interconnectedness of all people. Step 2: Analyze the options.
- (A) An Epitaph: Incorrect. This is not the source of the quote.
- (B) Fire-Hymn: Incorrect. The quote is not from *Fire-Hymn*.
- (C) Song of Myself: Correct. The line is from *Song of Myself* by Walt Whitman.
- (D) Sweetest Love I Do Not Goe: Incorrect. This is not the correct source of the quote. Step 3: Conclusion.
The correct source of the line is *Song of Myself*.