Detailed Instructions: 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".
Q: [header] How to treat heart disease in german shepherds [title] Look for a cough. [step] The most common sign of heart disease in a german shepherd is a cough. This usually occurs at night when the animal is resting. <sep> (A) Additionally, it can occur whenever the dog is outside. If your german shepherd has a strong cough, this is one to look for. (B) However, since dogs sometimes have these symptoms, it is very rare for their cough to become more serious. [substeps] If the dog eats solid food, then his cough may be more serious. (C) At this stage, the dog might cough more than usual because the dog is recovering from an anxiety attack. The cough itself is not quite visible in a german shepherd. (D) Fluid buildup in your dog's lungs may trigger a series of coughing fits. If your dog coughs for more than three days, you should take them to the vet.
A:
D