**Core Concept**
The question is testing the student's knowledge of the clinical significance and management of various types of fractures. The underlying principle being tested is the association of specific fractures with high mortality and morbidity.

**Why the Correct Answer is Right**
The correct answer is **C. Femoral shaft fracture**. Femoral shaft fractures are associated with high mortality and morbidity due to the potential for severe bleeding, compartment syndrome, and long-term disability. The femoral artery is located close to the fracture site, and bleeding from this artery can lead to significant blood loss. Additionally, the femoral nerve and blood vessels are at risk of injury, leading to potential long-term morbidity.

**Why Each Wrong Option is Incorrect**
* **Option A:** Hip fractures are a significant cause of morbidity and mortality in older adults, particularly due to the risk of osteoporosis and related complications. However, they are not as commonly associated with high mortality and morbidity as femoral shaft fractures.
* **Option B:** Tibial fractures are common and can be associated with significant morbidity, particularly if they are open or complex. However, they are not typically associated with high mortality and morbidity compared to femoral shaft fractures.
* **Option D:** Clavicle fractures are generally considered to be low-risk and have a good prognosis, with minimal long-term morbidity.

**Clinical Pearl / High-Yield Fact**
The "floating knee" is a term used to describe a fracture of both the femur and tibia, which can be associated with high morbidity and mortality due to the risk of compartment syndrome and bleeding.

**Correct Answer: C. Femoral shaft fracture**