Describe arch fingerprints.

Arch fingerprints are characterized by their unique pattern where the ridges enter from one side of the finger, create a raised wave or arch in the center, and then exit on the opposite side. This distinctive flow of the ridge lines is what differentiates arch patterns from other types of fingerprints, such as loops and whorls.

In contrast, the description involving a complete circle pertains to whorls, while random patterns are typically associated with irregular or unique fingerprints that do not adhere to defined classifications. Additionally, the flat arrangement of ridges with no curves does not accurately capture the typical structure found in arch fingerprints, which includes the rising wave in the center. Thus, the correct identification of arch fingerprints hinges upon recognizing the flow of ridges that cross in the center, forming a pronounced wave and allowing them to exit on the other side.