Correct Answer: (c) i-c, ii-a, iii-b
Solution:The pH of the human body ranges - 7 to 7.8, with the average at 7.40. The pH of the acid rain drops below 5.6 and it becomes ~ 4.2 β 4.4.
It mostly occurs due to the presence of oxides of sulphur and nitrogen in the atmosphere as nitrogen and sulphur oxides react with water vapour to form acids. When the pH in the mouth falls below 5.5, Bacteria present in the mouth produce acid by degradation of sugar and food particles which remain in the mouth after eating. The acid produced in the mouth attacks the enamel thereby, creating tooth decay.