The line graph illustrates the rate of ozone in one area during a day in four years, from 1982 to 2012.
Overall, the ozone levels experienced different trends in the time period. While the rate rose with some fluctuations in 1982 and 1992, the indication of ozone increased sharply in 2002 and 2012.
As the graph shows, the proportion stayed standly after midnight in four different years. In 1982 and 1992, there was a gradual rise of ozone during one day, it started at about 50 micrograms and finished at just under 100 at the end of the day.
Regarding the amount of ozone in 2002 and 2012, there was a stability of levels after 12 p. m. By contrast, they grew sharply from about 53 micrograms at 6 a. m. to more than 250 micrograms at midday. Then, the levels dropped suddenly to over 150 micrograms in four hours after 12 a. m. At the end of the day, the layers of ozone in one city witnessed a decrease, the lines stood at over 100 micrograms. 
The line graph illustrates the rate of ozone in one area during a day in four years, from 1982 to 2012.
 Overall
, the ozone levels experienced  
different
 trends in the time period. While the rate rose with  
some
 fluctuations in 1982 and 1992, the indication of ozone increased  
sharply
 in 2002 and 2012.
As the graph  
shows
, the proportion stayed  
standly
 after midnight in four  
different
 years. In 1982 and 1992, there was a gradual rise of ozone during one day, it  
started
 at about 50 micrograms and finished at  
just
 under 100 at the  
end
 of the day.
Regarding the amount of ozone in 2002 and 2012, there was a stability of levels after 12 p. m. By contrast, they grew  
sharply
 from about 53 micrograms at 6 a. m. to more than 250 micrograms at midday. Then, the levels dropped  
suddenly
 to over 150 micrograms in four hours after 12 a. m. At the  
end
 of the day, the layers of ozone in one city witnessed a decrease, the lines stood at over 100 micrograms.