A likely challenge that arose from the influx of workers into the sunbelt was inter race relations.
Population growth was another challenge of the sunbelt.Economic revival lured workers to the South & South West of Sunbelt which led to population growth.
Aging population was another challenge faced in the Sunbelt areas of the Southern part of USA.
Immigration was another challenge faced in the Sunbelt ares.
Noisy neighbours was another challenge.
So all the choices given 1,3 and 4 seem to be correct.