The correct answer is C. "I have never approved of the very public manner in which some of our western friends have conducted what they call the underground railroad, but which I think, by their open declarations, has been made most emphatically the upper-ground railroad."
Step-by-step explanation:
The Narrative of the Life of Frederick Douglass is a memoir in which the former slave and prominent abolitionist Frederick Douglas describes his experiences while being a slave and after this. Due to this, Douglass refers to issues during the 19th including the underground railroad that was a "secret" network of routes slaves used to scape.
The perspective of Douglass related to this topic can be seen in "I have never approved of the very public manner..." that shows Douglass does not approve this railroad "I have never approved of the very public manner" and the reason for this is that he believes the railroad is not secret and therefore dangerous "I think, by their open declarations, has been made most emphatically the upper-ground railroad". Thus, the excerpt that supports the inference Douglas believes the underground railroad is not secret and it is dangerous is the third excerpt.