A species of crayfish that lives in caves produces eyestalks like its above-ground relatives, but has no eyes. Eyestalks in cave-dwelling crayfish are thus                   . a. an evolutionary error; b. a dominant mutation; c. biogeographical evidence of evolution; d. a vestigial trait; e. evidence that evolutionary theory may be incorrect

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1. Identify the function of eyestalks in crayfish that live above ground, which is primarily to support and house the eyes for visual perception.
2. Consider the function of eyestalks in the cave-dwelling crayfish, which produce eyestalks but do not have eyes. Analyze whether these eyestalks serve any current function related to vision.
3. Understand the concept of a vestigial trait, which refers to anatomical structures or attributes that have lost most or all of their ancestral function in a given species.
4. Evaluate whether the presence of eyestalks without eyes in cave-dwelling crayfish fits the definition of a vestigial trait, considering they have a structure (eyestalks) that no longer serves its original function (supporting eyes for vision).
5. Choose the answer that best describes eyestalks in cave-dwelling crayfish based on the analysis of their functionality and comparison to the concept of vestigial traits.