**Core Concept**
Severe hypertension is a critical condition characterized by elevated blood pressure that poses a significant risk to patients' health. The definition of severe hypertension varies depending on the clinical context and guidelines, but it is generally considered a systolic blood pressure of 180 mmHg or higher or a diastolic blood pressure of 120 mmHg or higher.

**Why the Correct Answer is Right**
The correct answer is based on the American Heart Association (AHA) and the American College of Cardiology (ACC) guidelines for the management of hypertension. According to these guidelines, severe hypertension is defined as a systolic blood pressure of 180 mmHg or higher or a diastolic blood pressure of 120 mmHg or higher. This cutoff is used to identify patients who require immediate attention and aggressive blood pressure management to prevent complications such as cardiovascular damage, stroke, and kidney disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not align with the established guidelines for severe hypertension. The specified blood pressure levels are not supported by current clinical evidence.

**Option B:** This option is incorrect because it is too low to be considered severe hypertension. Blood pressures in this range may be considered elevated or stage 2 hypertension, but they do not meet the criteria for severe hypertension.

**Option C:** This option is incorrect because it is too high to be considered severe hypertension. While extremely high blood pressures can be life-threatening, they are not the cutoff for severe hypertension as defined by current guidelines.

**Clinical Pearl / High-Yield Fact**
It is essential for clinicians to recognize the importance of accurately diagnosing and managing severe hypertension to prevent long-term cardiovascular and renal complications. A prompt and aggressive approach to blood pressure management is critical in these cases.

**Correct Answer: B. 180/120**