Which species of insects have been released to control waterhyacinth, and which is most effective?

The choice highlighting the chevroned waterhyacinth weevil, mottled weevil, and waterhyacinth borer is accurate because these specific insect species have been identified as effective biological control agents for managing waterhyacinth, an invasive aquatic plant.

The chevroned waterhyacinth weevil feeds on the foliage of waterhyacinth and can significantly reduce the plant's growth. The mottled weevil also attacks the waterhyacinth, aiding in controlling its population. Meanwhile, the waterhyacinth borer larva tunnels into the plant's stem, which weakens the plant and can lead to its death. Collectively, these insects create a multi-faceted approach to controlling waterhyacinth and have been studied and confirmed for their effectiveness.

The other choices do not provide the same combination of insects that are primarily recognized for waterhyacinth control. While some insects might interact with aquatic environments, they do not have the specific efficacy against waterhyacinth that the selected species possess.