This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Injury to the Birth Canal, Subject name: Gynaecology & Obstetrics
[{'content': 'Following delivery, tear involves perineum, external anal spincter with intact mucosa, grade of tear is - \nSelect and explain. \nA. First degree, B. Second degree, C. Third degree, D. Fourth degree', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Third degree Classification of Obstetric Anal Sphincter Injuryo First degree : Injury to perineal skino Second degree : Injury to perineum involving perineal body (muscles) but not involving the anal sphinctero Third degree : Injury to perineum, involving the anal sphincter complex (both the external and internal).# 3a: if half thickness external anal sphincter involved.# 3b: if full thickness external anal sphincter involved.# 3c: if internal anal sphincter involoved.o Fourth degree : Injury to perineum involving the anal sphincter complex (external anal sphincter and internal anal sphincter) and anal epithelium.", 'role': 'assistant'}]