Which of the following insects is classified as beneficial?

The gray hairstreak is classified as a beneficial insect primarily because it is a type of butterfly that plays a vital role in pollination. Pollinators are crucial for the reproduction of many flowering plants, which in turn supports entire ecosystems and agricultural systems. The presence of such species contributes positively to both natural ecosystems and agricultural crop production by enhancing the yield and health of various plants.

In contrast, the other options include insects that are typically regarded as harmful or problematic. Fleas are known for being parasites that can transmit diseases, while flesh flies are associated with decaying matter and can pose issues regarding hygiene and health. Similarly, German cockroaches are notorious household pests that can contaminate food and surfaces, leading to potential health risks. Therefore, the beneficial nature of the gray hairstreak, combined with its ecological contributions, sets it apart from the other choices listed.