**Core Concept**
Diarthrosis, also known as synovial joints, are a type of joint that allows for a wide range of motion due to the presence of a synovial cavity and a joint capsule. These joints are characterized by the presence of a synovial fluid-filled space, which reduces friction between the articulating bones.

**Why the Correct Answer is Right**
Skull sutures, on the other hand, are a type of fibrous joint that connects the bones of the skull. Unlike diarthrosis, fibrous joints do not have a synovial cavity and instead rely on fibrous connective tissue to provide stability and support. The sutures in the skull allow for some degree of movement, but it is limited and restricted compared to diarthrosis. The absence of a synovial cavity and the presence of fibrous tissue are key characteristics that distinguish skull sutures from diarthrosis.

**Why Each Wrong Option is Incorrect**
**Option A:** The elbow joint is a classic example of a diarthrosis, with a synovial cavity and a joint capsule that allows for a wide range of motion.
**Option B:** Interphalangeal joints, which connect the bones of the fingers and toes, are also diarthrosis, characterized by a synovial cavity and a joint capsule.
**Option D:** The hip joint is a ball-and-socket diarthrosis, with a large synovial cavity and a joint capsule that allows for a wide range of motion.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the classification of joints is crucial in orthopedics, as it influences the type of injuries, diseases, and treatment options. Understanding the characteristics of different types of joints helps in making accurate diagnoses and developing effective treatment plans.

**✓ Correct Answer: C. Skull sutures**