The following are multiple choice questions (with answers) about medical knowledge.   **Question:** Etching depth after 30 sec for orthodontic bracket with orthophosphoric acid is:   (A) 10 μm — 20 μm   (B) 3 μm — 9 μm   (C) 50 μm — 110 μm   (D) 200 μm — 250 μm
['(A) 10 μm — 20 μm <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) 10 μm — 20 μm \n (B) 3 μm — 9 μm \n (C) 50 μm — 110 μm \n (D) 200 μm — 250 μm <> possible answers', '  Etching depth after 30 sec for orthodontic bracket with orthophosphoric acid is: <> context@']