**Core Concept**
The human skull is a complex bony structure that forms the upper part of the facial skeleton and the cranial vault. It is composed of multiple bones that fuse together during embryonic development and early childhood.

**Why the Correct Answer is Right**
The adult human skull is formed by 22 bones that are divided into two main groups: the cranial bones (8 bones) and the facial bones (14 bones). The cranial bones include the frontal bone, parietal bones, occipital bone, temporal bones, sphenoid bone, and ethmoid bone. The facial bones include the maxilla, zygoma, lacrimal bones, palatine bones, inferior nasal conchae, nasal bones, and mandible. These bones fuse together through a process called ossification, which allows the skull to develop its characteristic shape and structure.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately reflect the number of bones in the adult human skull. The correct number of bones in the adult skull is 22, not 20.
**Option B:** This option is incorrect because it overestimates the number of bones in the adult human skull. While there are 22 bones in the adult skull, there are not 25.
**Option C:** This option is incorrect because it underestimates the number of bones in the adult human skull. While there are 22 bones in the adult skull, there are not 19.

**Clinical Pearl / High-Yield Fact**
It's worth noting that the number of bones in the human skull changes throughout life, with some bones fusing together during childhood and adolescence. This process of bone fusion is an important aspect of normal skeletal development.

**Correct Answer:** C. 22