Cluster headaches are characterized by attacks that:

• A. Attacks come in groups; more men than women experience this
• B. Occur singly with no pattern
• C. Occur only during sleep
• D. Are caused by dehydration

Answer: (A)

Cluster headaches are defined by attacks that occur in repeated bouts or clusters, with many attacks occurring over a short period (weeks to months) followed by long remission periods. This episodic clustering is the hallmark, and there is a notable male predominance in affected individuals, which is why this option best fits. The other statements don’t match the pattern: attacks are not simply isolated with no rhythm, they’re not confined to sleep (they may disturb sleep but aren’t limited to it), and dehydration is not a causative factor.