Expository writing traditionally serves the purpose of giving some sort of information. Either through describing, informing, or explaining the audience about a specific topic
I think that absolute phrases are the underlined element in this passage by Charles Dickens.
The following ones can be identified: “… flowing up the river […] city”, “…rolling down the river […]city”. Absolute phrases happen when a noun and a participle (in this case the present participle –ing) function as an independent clause. In this case, they describe the clause, the manner of the movement of the fog.
the answer is not c. I don't know what the answer is but it isn't c