Tooth enamel begins to corrode when the pH of the mouth falls below: (A) 7.0 (B) 6.0 (C) 5.5 (D) 4.5

Question

Tooth enamel begins to corrode when the pH of the mouth falls below:
(A) 7.0
(B) 6.0
(C) 5.5
(D) 4.5

Accepted Answer

## Model Answer **(C) 5.5** Tooth enamel begins to corrode when the pH of the mouth falls below **5.5**. Source: Chapter 2, Section 2.3.1 (pH change as the cause of tooth decay) --- ## Explanation The textbook explicitly states: *"Tooth decay starts when the pH of the mouth is lower than 5.5."* This is a direct recall fact — memorise the exact value 5.5, not 7 (neutral) or any other option. Examiners frequently ask this as a 1-mark MCQ or fill-in-the-blank.

Science (086) — AI-generated practice question