The given graph represents the production of fuel in the United Kingdom from 1981 to 2000. As we look at the graph, the blue line represents petroleum, the orange dotted line shows natural gas, and the gray line represents coal.
It is evident that petroleum has been the most used fuel from both natural gas and coal until 2000. From the year 1981 to 1986, the consumption of approximately 90 to 140 energy units. From 1986, the usage decreased to 100 energy units, and then again, it raised to steadily 140 energy units until 2000.
In the early years, coal was at a good rate of around 80 energy units but it decreased from 1986 until 2000 to less than 40 energy units.
As far as natural gas is concerned, its usage from 1981 to 1990 was the lowest among others with approximately 40 energy units. Since 1990, consumption has increased steadily to more than 100 energy units until 2000.
Overall, petroleum was the most used fuel among the other two fuels i.e., coal and natural gas. the usage of coal decreased with time while the demand for natural gas increased.