The following are multiple choice questions (with answers) about medical knowledge.   **Question:** Ionic exchange between enamel surface and environment:   (A) Does not take place once enamel matures   (B) Stops after 2 years of eruption   (C) Continues till adult life   (D) Continues through out life
['(D) Continues through out life <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) Does not take place once enamel matures \n (B) Stops after 2 years of eruption \n (C) Continues till adult life \n (D) Continues through out life <> possible answers', '  Ionic exchange between enamel surface and environment: <> context@']