I would say the agricultural aspect of how the Mayans grew their crops. I learned this unit just a few months ago and even a bit before. This article has a lot on the Mayan culture.
Source: www.history.com/topics/maya
Um i’m not sure i just answered for the points
They operate, maintain or repair geothermal power plants and commercial and residential geothermal heating installations. (googled this for you)
The answer is C. Battle of Palmito Ranch because Robert E. Lee, the last land action of the civil was took place at Palmito Ranch near Brownsville.