The figure shows the consumption of fast food by Australian Teenagers from 1975 to 2000. In general, the consumption of hamburgers and pizza has increased a lot from less than 20 times per year to more than 80 or even 100 times per year. However, fish and chips has experienced a rapid decrease from about 100 times per year to less than 40 times per year. The consumption of fish and chips has a brief rise between 1980 and 1985, while it continues to decline since then. 1985 is also the time when the consumption relationship between fish and two other junk foods changed. Before 1985, teenagers eat more fish and chips, then they prefer hamburgers to the previous 2 kinds of junk food and at about 1990 the consumption of hamburgers also overtook the fish and chips. Besides, pizza consumption grew faster and faster until it leveled off after 1995 and hamburger growth gradually slowed down and it also stabilized around 1995. From the trend in the figure, the fish are mo...