**Core Concept**
Cluster headaches are a type of primary headache disorder, characterized by severe, unilateral orbital, supraorbital, or temporal pain lasting from 15 minutes to three hours, occurring in clusters or cyclical patterns. This condition is more common in males.

**Why the Correct Answer is Right**
Cluster headaches predominantly affect males, with a male-to-female ratio of approximately 2.5:1. The exact cause of this gender disparity is unclear, but hormonal and genetic factors may play a role. The high prevalence of cluster headaches in males is thought to be related to the presence of the HLA-A*02:01 allele, which is more common in men.

**Why Each Wrong Option is Incorrect**
**Option B:** Cluster headaches are indeed characterized by unilateral headache, typically on one side of the head, often in the same location on each attack.
**Option C:** Onset of cluster headaches typically occurs in the third to fifth decade of life, which is around 20-50 years of age.
**Option D:** Cluster headaches are associated with autonomic symptoms, including conjunctival congestion, lacrimation, rhinorrhea, and nasal congestion, due to the activation of the trigeminal nerve.

**Clinical Pearl / High-Yield Fact**
Cluster headaches are often referred to as "suicide headaches" due to their intense pain, which can be so severe that patients may attempt to self-medicate or even take their own lives. It is essential for clinicians to recognize the characteristic features of cluster headaches and provide prompt, effective treatment to alleviate suffering.

**✓ Correct Answer: A. Affects predominantly females.**