Which best explains why a decrease in the types of insects in an ecosystem reduces the sustainability of the ecosystem?

Organisms that depend on insects may not survive, eventually harming all the organisms that are interconnected.
The biodiversity of the ecosystem cannot be protected by laws unless there are a certain number of insect species.
There will likely be fewer insects that harm plants, causing an increase in plant diversity.
Having fewer insects allows other organisms to use the resources that the insects were using.