Which plant features green, ribbon-like leaves with small whitish-yellow flowers visible in late summer?

The answer identifies wild celery as the plant characterized by green, ribbon-like leaves and small whitish-yellow flowers that bloom in late summer. Wild celery, or Vallisneria americana, typically grows in shallow waters and is known for its elongated, strap-like leaves that can create a ribbon-like appearance. In addition to its distinct foliage, wild celery produces small flowers that can vary in color but are often noted for their whitish-yellow tones, making them less conspicuous, especially at a distance.

The other options do not share this combination of features. Coontail, for example, consists of grouped, bushy formations rather than ribbon-like leaves and lacks prominent flowers. Sago pondweed has broader leaves and produces various types of flower structures that do not match the description given. Southern naiad features more serrated and elongated leaves but is also not known for producing the described flowers. This context clarifies why the characteristics of wild celery align with the details provided in the question.