Final answer:
The disadvantage of flatworms reproducing through fragmentation, an asexual reproduction method, is a lack of genetic diversity. This uniformity can lead to an increased risk of extinction if the environment changes, as all offspring are genetic clones of the parent.
Step-by-step explanation:
The question posits what could be a disadvantage of flatworms reproducing through fragmentation, which is a form of asexual reproduction. A disadvantage of asexual reproduction, like fragmentation, is its genetic diversity. When organisms reproduce asexually, their offspring are genetically identical clones of the parent. This genetic uniformity can be a significant drawback because it means that if environmental conditions change, the chance that any individuals will have adaptations to survive is exceedingly low.
Therefore, the correct answer to the student's question is A. Genetic diversity. This is because a lack of genetic variation in a population means that there may be no individuals that can survive sudden or significant changes, increasing the risk of extinction for the species.