Answer: a) urban areas
Explanation:
The reason for these migrations was not the imminent threat of war, the natural catastrophe and fear of famine, as is the case with immigration. The goal is the primarily unfortunate economic situation, racial segregation, and discrimination. Better living conditions have forced a vast population to migrate. During the twentieth century, two significant waves of migration occurred. One in the period from 1910 to 1940 and the other after the end of World War II until 1970.
A pure substance is something that occurs in nature. An element is made up of one type of atom only and cannot be split further.
In simpler terms it is true an element is a substance that is made of ONE type of atom
Macroeconomics is a branch of economics that studies how the aggregate economy behaves. A variety of economy-wide phenomena is examined such as, inflation, price levels, rate of growth, national income, gross domestic product (GDP), and changes in unemployment.
If you still don't understand I recommend watching this https://www.youtube.com/watch?v=d8uTB5XorBw