Answer:
Petroleum is relatively inexpensive compared to other forms of energy.
Step-by-step explanation:
Because:
"Natural gas does not produce greenhouse gases as other energy sources do." natural gas does produce greenhouse gases, including carbon dioxide and water vapor, the natural gas mostly releases the greenhouse gas.
"Coal deposits are found on nearly every continent and mining coal poses few risks." coal is inexpensive, but could be damaging to the habitats around the coal mining.
"Nuclear power increases water vapor in the atmosphere." nuclear powder doesn't really increase water vapor, but makes water vapor.
"Petroleum is relatively inexpensive compared to other forms of energy." it is inexpensive if compared to other fossil fuels. (aka, the most inexpensive)