Many people migrated from north and east to the sun belt states during the 1950 because of

C: the interstate highway system

Explanation:

edg2021

The answer is NOT B. Here is a direct quote from an EDG instruction video:

". A further push to the new car culture came when Congress passed the Federal Aid Highway Act in 1956. The act allowed faster transportation across America, helping businesses and making trucking an important way to transport goods. And it helped to add freeways to cities, which encouraged suburbs to grow. Cities and their downtowns had suffered as people began to move out to the suburbs. The new highways dealt another blow to cities because the new highway systems often went around the cities instead of through them. During the 1950s, in part because of the new highway system, another migration was taking place. In addition to moving from the cities to the suburbs, Americans began moving from the northern and eastern states to the warmer and southern western states. This new era of settlement was called the Sun Belt. This migration pattern was in its early stages during the 1950s.

it says exactly, "...in part because of the new highway system, another migration was taking place... This new era of settlement was called the Sun Belt."