Which growth regulators are explicitly noted for harmful environmental contamination?

The correct choice emphasizes the environmental risks associated with certain growth regulators. Tordon, Transline, and Vista are known for their potential to cause significant environmental contamination due to their persistence and mobility in various ecosystems.

Tordon, for instance, is a broad-spectrum herbicide that can remain in the environment for a prolonged period, making it likely to affect non-target species and contaminate water sources. Transline is known for its effectiveness against certain weeds but also poses risks related to its potential to leach into groundwater. Vista, while effective in managing specific vegetation, similarly has a history of environmental concerns related to runoff and non-target effects.

These risks highlight the importance of understanding the environmental impact of using specific herbicides and growth regulators, making cautions such as ensuring proper application methods and timing essential in minimizing harm to the ecosystem. The other choices involve growth regulators and herbicides that, while they may have certain concerns, are not cited with the same level of environmental contamination risk as Tordon, Transline, and Vista. Understanding these distinctions is crucial for responsible herbicide use and maintaining environmental health.