Answer:
The correct answer to the question: Where did most coal mining take place before 1907, when the Indian Territory´s mining industry was still developing? would be, C: Choctaw land.
Step-by-step explanation:
The mining industry, at least the bulk of it, develped in the state of Oklahoma, from the 1870´s, when it was started commercially by James J McAlester, and with the appearance of the railroads. This particular industry started developing when McAlester found some of this mineral in his recently bought land in Oklahoma. After that, he dedicated himself to find maps that identified possible locations for the mineral, and after finding that most of it was inside Choctaw land, he married into the tribe and developed its mining process and also its commercial distribution.