Teacher:In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".
Teacher: Now, understand the problem? Solve this instance: [header] How to identify heart blocks [title] Understand what the term " heart block " refers to. [step] The term heart block refers to an av block or an atrio-ventricular block. This is when there is some obstacle blocking electrical signals between the upper and lower chambers of the heart. <sep> (A) Av blocks are a longer term term, for instance called " heart block ". [substeps] Heart block blocks are usually black, which means that there is not a hair block or an artery. (B) These signals are not evident on the inside of the heart block. A heart block that is present in your heart block may not be heart block but another heart block which trains the arteries in the heart muscles. (C) The lack of these signals is known as an av block. Av blocks are what appear to alter arteries in the heart. (D) [substeps] There are three degrees of av block according to severity-first degree, second degree and third degree. Second degree heart blocks have two subtypes.
Student:
D