The following are multiple choice questions (with answers) about medical knowledge.   **Question:** Which of the following is used for etching porcelain?   (A) 1.23% HF   (B) 4% HF   (C) 9.6% HF   (D) 37% HF
['(C) 9.6% HF <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) 1.23% HF \n (B) 4% HF \n (C) 9.6% HF \n (D) 37% HF <> possible answers', '  Which of the following is used for etching porcelain? <> context@']