For the united states, the primary fuel that we use for our energy is for the united states, the primary fuel that we use for our energy is coal nuclear oil natural gas wood

Natural gas accounts for the most used source of energy  in the usa. natural gas is used in homes, and to generate electricity. according to research, 37 percent of energy consumption in the USA is from this form of primary energy.
it is followed by oil,coal and nuclear energy.  Wood is a rare source of energy in the country. Renewable sources of energy include solar and wind energy.

Did you know it's illegal to own only one guinea pig in switzerland?   : )

The answer is c, i, iii, and iv. this is because farming and mining deal with harvesting raw materials, construction work falls under manufacturing, and piloting a plane is a service. ii is wrong because making bread is using  raw materials to produce goods, which would fall under the secondary sector, not primary.