30. Many cities in the northern hemisphere have poor east end districts.What can be considered to be a generalized reason for the concentration of poorgroups always ending up in the east of these cities?
(A) downstream location at major river which took city’s waste and smell eastward
(B) later sunrise in the east compared to the western part of these cities
(C) prevailing winds are westerlies, blowing pollution to the east
(D) distribution of the urban heat island, which is eastward biased