Which of the following statements is not true?_x005F_x000D_

• A. Bacteria present in the mouth produce acids by degradation of sugar and food particles remaining in the mouth.
• B. When pH of the mouth is higher than 5.5. then tooth decay starts.
• C. Tooth enamel made of calcium phosphate is the hardest substance in the body.
• D. Using toothpaste, which are generally basic, helps neutralise the excess acid and prevent tooth decay.