Final Answer:
The plains of South Texas were transformed forever due to B) the discovery of a valuable resource.
Step-by-step explanation:
Discovery of Valuable Resource: The correct option is B) "The discovery of a valuable resource." The transformation of the plains in South Texas can be attributed to the discovery of valuable resources, such as oil. The oil boom in the region led to significant economic and demographic changes, attracting industries and population influx.
Explanation for Option B: The discovery of oil brought about a rapid and profound transformation in the South Texas plains. The extraction and exploitation of this valuable resource led to the establishment of oil-related industries, infrastructure development, and an economic boom.
The region experienced increased economic prosperity, urbanization, and population growth as a result of this resource-driven transformation.
The plains of South Texas were transformed forever due to B) the discovery of a valuable resource.