**Core Concept**
Obesity is a complex condition characterized by excess body fat, leading to various physiological and anatomical changes that increase the risk of several complications. These complications arise from the mechanical effects of excess weight, metabolic changes, and the strain on multiple organ systems.

**Why the Correct Answer is Right**
The correct answer encompasses the diverse range of complications associated with obesity. **Option 1**, venous ulcer, is a consequence of chronic venous insufficiency, which is exacerbated by the increased pressure and strain on the veins due to excess body weight. **Option 2**, pulmonary embolism, is a potential complication of obesity due to the increased risk of deep vein thrombosis (DVT), which can dislodge and travel to the lungs. **Option 3**, Pickwickian syndrome, is a rare condition characterized by obesity, hypoventilation, and hypoxemia, leading to pulmonary hypertension and other complications. **Option 4**, hernias, are a common complication of obesity due to the increased intra-abdominal pressure. **Option 5**, pulmonary hypertension, is a potential complication of obesity, particularly in the context of Pickwickian syndrome.

**Why Each Wrong Option is Incorrect**
* **Option A**: This option is incorrect because it excludes pulmonary hypertension, which is a recognized complication of obesity.
* **Option B**: This option is incorrect because it excludes venous ulcer, a well-documented complication of obesity.

**Clinical Pearl / High-Yield Fact**
Obesity is a significant risk factor for the development of multiple complications, including those affecting the cardiovascular, respiratory, and musculoskeletal systems. It is essential for clinicians to be aware of these potential complications and to address obesity as a primary concern in the management of patients with excess body weight.

**✓ Correct Answer: D. All are true**