Which of the following is classified as a general disqualification for lack of breed characteristic?

Marbled eyes are classified as a general disqualification for lack of breed characteristic because breed standards for rabbits often specify particular eye colors and appearances that are characteristic of that breed. When a rabbit displays marbled eyes, it indicates a deviation from those established breed standards, which can detract from the rabbit's overall conformity to the breed. This disqualification helps maintain the integrity and consistency of breed characteristics in competitions.

In contrast, tumors, fleas, and hiccups are typically associated with health issues rather than breed characteristics. Tumors are medical conditions that affect the health of the rabbit, while fleas are external parasites that can be treated. Hiccups are a physiological occurrence that does not reflect on the breed standard and are not factors considered in evaluating the breed characteristics of a rabbit. Thus, only marbled eyes directly relate to a lack of breed-specific features, making it the correct choice in this context.