In contrast to historical trends: A) Current higher levels of urbanization are necessarily equivalent to higher levels of income as people move from the rural areas into the cities in search for better living conditions B) Developed countries today, have the largest cities in the world in terms of the population size C) Current higher levels of urbanization are not necessarily equivalent to higher levels of income as many migrants now move from the rural areas into the cities and live under conditions of extreme poverty D) Both a and b are correct