**Core Concept**
Venous thrombosis refers to the formation of a blood clot within a vein, which can lead to obstruction of blood flow and potentially life-threatening complications. The development of venous thrombosis is influenced by various factors, including patient demographics, medical conditions, and environmental factors such as hospital admission.

**Why the Correct Answer is Right**
Hospital admission is a significant risk factor for the development of deep venous thrombosis (DVT). This is due to prolonged immobilization, which increases the risk of blood stasis and clot formation. Additionally, hospitalization often involves invasive procedures and medical conditions that further contribute to the risk of DVT. The Virchow's triad, which includes blood flow stasis, hypercoagulability, and endothelial injury, is often disrupted in hospitalized patients, making them more susceptible to DVT.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement is incorrect because venous thrombosis can affect both the deep and superficial venous systems. While DVT primarily affects the deep veins, superficial thrombophlebitis can occur in the superficial veins.
**Option C:** This statement is incorrect because a coralline thrombus is actually a type of arterial thrombus that is characterized by a branching, coral-like pattern. In contrast, DVT typically forms as a platelet-rich thrombus surrounded by fibrin.
**Option D:** This statement is incorrect because lung infarction is a complication of pulmonary embolism (PE), not DVT. While DVT can lead to PE, lung infarction is a more direct consequence of a large PE causing infarction of lung tissue.

**Clinical Pearl / High-Yield Fact**
The Wells' score is a clinical prediction rule that can help identify patients at high risk for DVT. It takes into account factors such as active cancer, recent surgery, and immobilization to estimate the likelihood of DVT.

**✓ Correct Answer: B. Most impoant factor for development of deep venous thrombosis is hospital admission**