Answer:
Underground Railroad.
Explanation:
Slavery was abolished by President Lincoln, but many slaves did free themselves and go north. If they reached the north they were free, so that's what they did. The Underground Railroad wasn't actually a railroad, it was a secret code to a path that went north. One of the post famous "conductors", someone who helped fellow slaves escape to the north, was Harriet Tubman.
B. No , because average Egyptians were used as slaves to build the temples and pyramids
For 1 because there were many things like gold, silk, and spices in places in the west that were not in the east
I wonder whether there would be also other options, but one very important aspect is the smog: the city center is where many industry-relevant things meet: the factories are all around it, transport, cars... and since it is surrounded by bad air, the air takes longer to dissipate. This is especially visible if the city is in a valley, such as Mexico city foe example.
