**Core Concept**
Essential hypertension is a chronic medical condition characterized by elevated blood pressure levels in the absence of any identifiable secondary cause. It is a multifactorial disorder involving the interplay of genetic, environmental, and lifestyle factors.

**Why the Correct Answer is Right**
The most common feature of essential hypertension is the presence of **hypertensive target organ damage**, particularly to the kidneys, heart, and blood vessels. This is due to the prolonged exposure of these organs to elevated blood pressure, leading to changes in their structure and function. The kidneys are often the first to be affected, with changes including **renal vascular hypertrophy**, **glomerular sclerosis**, and **renal fibrosis**. The increased workload on the heart also leads to left ventricular hypertrophy, which can increase the risk of heart failure and arrhythmias.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because while orthostatic hypotension can be a feature of some secondary hypertension cases, it is not a common feature of essential hypertension.
* **Option B:** This option is incorrect because while a family history of hypertension can increase an individual's risk, it is not a feature of the condition itself.
* **Option D:** This option is incorrect because while physical inactivity can contribute to the development of essential hypertension, it is not a feature of the condition.

**Clinical Pearl / High-Yield Fact**
Essential hypertension is often referred to as the "silent killer" because it can progress to target organ damage without noticeable symptoms, making regular blood pressure monitoring and early detection crucial.

**Correct Answer:** C. Hypertensive target organ damage