Regional urban centers face these challenges.

"These issues present challenges for regional urban areas: housing availability, pollution and rural migration. Housing availability is one, because there are many people looking for housing in those areas, pollution because urban centers often have industrial sites where toxic fumes are released into the air, as well as transportation pollution and rural migration, because people from rural areas come to urban areas often to look for jobs."

I do not own this paragraph.  This person does..

Explanation:

a characteristic is a deep cut in the earth or left over rock aka till.  

answertemperature;