<span>It is to protect the American state and its interests abroad</span>
The greeks are surrounded by sea, making it easier for them to built fort-based city. This type of city organization of course couldn't be done by the persians that's surrounded by desert. Hope This Helps!
I'm pretty sure its D not fully sure
They operate, maintain or repair geothermal power plants and commercial and residential geothermal heating installations. (googled this for you)