In Whitman's poem "O Captain! My Captain!" , in the first line "our fearful trip is done", what does the trip refer to?
A.
The fighting of American people for independence.
B.
The Civil War, in which people in American fight for equality, democracy and the liberation of slaves.
C.
The journey they made when escaping Britain.
D.
A great deed they fulfilled as winning over the south of Amerca and reunited the country together.