A specific location in America produces electricity from fossil fuels and geothermal energy. The table below shows the amount of carbon dioxide in the atmosphere of the location from 1960 to 2000. Year19601970198019902000
Carbon dioxide concentration (in parts per million by volume)317325339318328

Based on the table, which of these conclusions is most likely correct?
In 1990, electricity was generated only from fossil fuels.
In 1980, electricity was generated only from geothermal energy.
Between 1960 and 1970, there was an decrease in the use of geothermal energy.
Between 1980 and 1990, there was a decrease in the use of geothermal energy and an increase in the use of fossil fuels.