D

Reasoning: Flukes that produce large ova (>100 µm) include Fasciola gigantica (~130–150 µm), Gastrodiscoides hominis (~150 µm), and Echinostoma ilocanum (~130–150 µm). In contrast, Opisthorchis viverrini lays much smaller eggs, only about 26–30 µm in length, so it would not account for the >100 µm ova seen in the stool [Valero 2009, PMID 19375410; Sukontason 1999, PMID 10774711].