What is a defining characteristic of the hairline in Dutch rabbits?

The defining characteristic of the hairline in Dutch rabbits is a narrow white line. This distinctive feature, often referred to as a "band," runs along the face and connects to the coloration of the body, creating a specific appearance that is unique to the breed. The narrow white line helps in identifying Dutch rabbits and contributes to their overall aesthetic appeal.

In contrast, the other options describe traits that are not specific to Dutch rabbits. A broad dark stripe might be present in other breeds but doesn’t define Dutch rabbits. A colored blaze could be found in various breeds, and a fully furred head can be an attribute of many rabbit types. However, the narrow white line is specifically tied to the breed standard of Dutch rabbits, making it the correct answer.