**Core Concept**
Marital status is a significant risk factor for suicide, particularly among the unmarried. This association is often attributed to the lack of social support, increased stress, and feelings of isolation that can accompany single or unmarried status.

**Why the Correct Answer is Right**
Being unmarried is a known risk factor for suicide due to various factors. Unmarried individuals often lack a supportive partner, which can exacerbate feelings of loneliness and depression. Moreover, unmarried individuals may have fewer social connections and a reduced sense of belonging, further increasing their vulnerability to suicidal ideation. Studies have consistently shown that unmarried individuals, particularly those who are divorced or separated, have a higher risk of suicide compared to their married counterparts.

**Why Each Wrong Option is Incorrect**
* **Option A:** Female sex is actually a risk factor for attempted suicide, but not necessarily completed suicide. Women are more likely to attempt suicide, while men are more likely to complete the act.
* **Option C:** Age 30 years is not a specific risk factor for suicide. While suicide risk does increase with age, particularly among older adults, age 30 is not a particularly vulnerable age group.
* **Option D:** Being married is actually a protective factor against suicide. Married individuals tend to have stronger social connections, better mental health, and a reduced risk of suicidal behavior.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that marital status is just one of many risk factors for suicide. Other factors, such as a history of mental illness, substance abuse, and social isolation, must also be considered when assessing an individual's suicide risk.

✓ Correct Answer: B. Unmarried