Science Dict 1B Ch.5.3

__________ are our major energy source. They include coal, crude oil and natural gas.

Fossil fuels cannot be replaced in a short period of time once they are used. They are
_________________

When air pollutants like sulphur dioxide and nitrogen oxides dissolve in rainwater, ___________may form.

The burning of fossil fuels gives out a large amount of carbon dioxide and nitrogen oxides. More thermal energy is trapped in the atmosphere. This enhances the _________________.

The average air temperature gradually increases. This is called
____________.

Solar energy, wind power, biomass energy, hydroelectric power are _________________.