Identify each prepositional phrase in the following passage from Mark Twain's Life on the Mississippi. Then, indicate which question each phrase answers.

Sometimes, in the big river, when we would be feeling our way cautiously along through a fog,
the deep hush would suddenly be broken by yells and a clamor of tin pans, and all in an instant a
log raft would appear vaguely through the webby veil, close upon us