Which of the following headaches is characterized by unilateral, severe pain and associated watering of the eye?

The correct choice is characterized by unilateral, severe pain and is closely associated with autonomic symptoms, including watering of the eye. This type of headache is known as a cluster headache.

Cluster headaches are often described as one of the most painful headache types. They typically occur in cyclical patterns or "clusters," meaning that the sufferer may experience frequent attacks over a period of weeks or months, followed by periods of remission. The pain is usually localized around one eye or temple and can be accompanied by other significant symptoms—specifically, tearing and nasal congestion on the affected side, which further contributes to the distinguishing features of this type of headache.

Understanding these attributes is crucial for differentiation from other types of headaches. For instance, while migraines can also cause unilateral severe pain, they are more commonly accompanied by other symptoms such as nausea and light sensitivity rather than autonomic features like eye watering. Thunderclap headaches are sudden, intense headaches that can indicate serious conditions like hemorrhaging and do not typically present with watering of the eye. Post-traumatic headaches may vary in presentation and are generally tied to previous trauma rather than the acute, cyclical pattern observed in cluster headaches. Thus, the unique characteristics of cluster headaches make them the correct answer to the question