interpreting a graph

model answer: Anyone who has visited a dentist has been told that eatingexcessive amounts of sweets risks harming the teeth. This isbecause sweets lower pH levels in the mouth to dangerous levels. When the pH level in the mouth is kept above 5.5, acidity is suchthat teeth are unlikely to be in danger of decay. Sweet foods,however, cause pH in the mouth to drop for a time, and thelonger pH levels remain below 5.5, the greater the opportunity fordecay to occur. By comparing fruit sugar, cane sugar and honey, which are allcommon ingredients of sweet foods, we find that cane sugarlowers pH levels for the longest period, thus producing thegreatest risk of the three. Approximately five minutes afterconsuming cane sugar, pH levels drop to as little as pH 3.5. Theythen begin to rise slowly, but do not rise above pH 5.5 until atleast 30 minutes have elapsed. By contrast, fruit sugar, whichcauses the mouth's acidity to fall to just above pH 4, poses adanger for a shorter period: tooth decay is unlikely 20 minutesafter consumption. Honey appears an even less risky substance.Though acidity falls to about pH 4.75 within five minutes ofconsumption, it returns to above pH 5.5 in under fifteen minutes. The implications, then, are that people who insist on eating sweetfoods should be aware of the ingredients, and that fruit sugar orhoney appear preferable to cane sugar. (242 words)