The ethnic makeup of the andes and the pampas a has little diversity. b has had no influence on the history of the region. c is almost entirely descended from spanish conquistadors. d is greatly influenced by the geography of the region.

The correct answer is A. Has little diversity.
The Andean and Pampas regions are a very wast space, but they have remained relatively isolated space when it comes to ethnic mixture and diversity. The European colonist preferred the coastal regions and the lowlands, because they were the best places for trade, agriculture and farming. Apart from being under a foreign ruler, the people from the Andean and Pampas regions didn't faced assimilation, and only small percentage mixed with the newcomers, so till this day, the people that live in here are descendants of the native people from this regions and have very little to none admixture.

Answer(a); // soil salinization and waterlogging;