Question

cooperative trees
we often think of trees as simple objects that provide us with things we need, such as lumber, shade, or fruit. yet trees are far more complex—and social—than we recognize. an underground network of fungi, which some have called the \wood - wide web,\ connects the roots of numerous trees in a forest. using the network, trees can communicate with and support one another. they may share water, carbon, nutrients, and protective compounds with one another. scientists believe that one explanation for this phenomenon may be a \source - sink model.\ according to this theory, trees growing in excellent conditions with many resources transfer these resources to trees growing in less favorable conditions. in this way, trees in a forest ensure the health of the entire community by working cooperatively.
what is the main, or central, idea of the passage?
trees in a forest work to support one another by using an underground fungal network.
the wood - wide web is an underground fungal network of connections between trees.
different parts of a forest may provide different conditions for trees, some more and some less favorable for growth.

Explanation:

The passage starts by challenging the common - simple view of trees, then introduces the wood - wide web (an underground fungal network) that connects trees. It explains how trees use this network to communicate, support each other, share resources, and maintain the health of the forest community. The main focus is on the cooperative behavior of trees via the fungal network.

Answer:

Trees in a forest work to support one another by using an underground fungal network.