**Core Concept**
The question is testing the student's knowledge of the anatomy of the pelvis, specifically the type of joint between the sacrum and the coccyx. The sacrococcygeal joint is a cartilaginous joint that connects the sacrum to the coccyx, allowing for limited movement.

**Why the Correct Answer is Right**
The sacrococcygeal joint is a type of synsacrum, which is a cartilaginous joint that is formed by the fusion of the sacrum and the coccyx. This joint is unique in that it is a transitional zone between the sacrum, which is a fused vertebra, and the coccyx, which is a separate bone. The joint allows for limited movement, such as during childbirth, when the baby's head passes through the pelvis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the sacrococcygeal joint is not a synovial joint, which is characterized by a fluid-filled space between the articulating bones.
**Option B:** This option is incorrect because the sacrococcygeal joint is not a fibrous joint, which is characterized by fibrous connective tissue between the articulating bones.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the sacrococcygeal joint is a weak point in the pelvis, and injuries to this area can be painful and may require surgical intervention.

**Correct Answer:** C. Synsacrum