The following are multiple choice questions (with answers) about medical knowledge.   **Question:** Decalcification and discoloration of teeth occurs during orthodontic treatment due to:   (A) Acid etching   (B) Poor oral hygiene   (C) Leakage of cement around bands   (D) All of the above
['(D) All of the above <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) Acid etching \n (B) Poor oral hygiene \n (C) Leakage of cement around bands \n (D) All of the above <> possible answers', '  Decalcification and discoloration of teeth occurs during orthodontic treatment due to: <> context@']