i guess the cause and effect would show how being around the smoke(the cause) can have negative effects on the body.
In City, it can be inferred from the author's choice to include drawings of tools used by ancient Roman city builders that:
B. He wants to show that modern builders use many of the same tools that the ancient Romans used.
In this way, he wants to make a standpoint that the tools used by ancient Roman city builders are proven useful then and now.