Final answer:
The author uses 'it' to convey a sense of the unknown and unfamiliar, reflecting the characters' experience in a novel and industrial environment they are unable to fully understand. Option b.
Step-by-step explanation:
The author's frequent use of 'it' is employed to create a sense of the unknown and unfamiliar, reflecting the perspective of the passengers who are entering a new environment. This term encapsulates the unknown odor and atmosphere of the industrial city they are approaching, which is a stark contrast to their homeland.
By referring to the odor as 'it', the author allows readers to share in the characters' initial experience of confusion and curiosity, emphasizing how the characters are entering an alien and ominous environment that they cannot yet fully comprehend or name.
So option b