Answer:
I would say natural gas and coal.
Due to its factories and mining facilities
<span>The success of the Roman army is mainly attributed to a well-trained army as well as meticulous planning prior to each assault. The Roman army also used a highly successful attack technique that utilized a combination of long and short range attacks utilizing legionnaires wielding both a pila and gladius</span>
The answer is b. the gravitational pull on materials of varying densities.