Final answer:
Stephen can bring a valid claim against the textiles plant if the runoff has caused substantial damage to his property.
Step-by-step explanation:
In order for Stephen to bring a valid claim against the textiles plant for public nuisance, he would need to establish legal standing. Legal standing means that Stephen has a sufficient connection to the issue in order to bring a claim. Out of the options provided, the one that would permit Stephen to bring a valid claim is option D, where the runoff from the textiles plant has caused substantial damage to Stephen's property. This would give Stephen the legal standing to seek compensation for the damage caused.