The following are multiple choice questions (with answers) about medical knowledge.   **Question:** In which of the following case Hamman's sign is seen?   (A) Hematoma   (B) Accidental  NaOCl   (C) Pneumomediastinitis   (D) Oral carcinoma
['(C) Pneumomediastinitis <> answer', 'The following are multiple choice questions (with answers) about medical knowledge. <> instruction', '(A) Hematoma \n (B) Accidental  NaOCl \n (C) Pneumomediastinitis \n (D) Oral carcinoma <> possible answers', "  In which of the following case Hamman's sign is seen? <> context@"]