Question

years ago, i stumbled across a patch of strangely looking mossy stones in one of the preserves of old beech trees that grows in the forest i manage. casting my mind back, i realized i had passed by them many times before without paying them any heed. but that day, i stopped and bent down to take a good look. the stones were an unusual shape: they were gently curved with hollowed - out areas. carefully, i lifted the moss on one of the stones. what i found underneath was tree bark. so, these were not stones, after all, but old wood. i was surprised at how hard the \stone\ was, because it usually takes only a few years for beechwood lying on damp ground to decompose. but what surprised me most was that i couldnt lift the wood. it was obviously attached to the ground in some way.
i took out my pocketknife and carefully scraped away some of the bark until i got down to a greenish layer. green? this color is found only in chlorophyll, which makes new leaves green; reserves of chlorophyll are also stored in the trunks of living trees. that could mean only one thing: this piece of wood was still alive! i suddenly noticed that the remaining \stones\ formed a distinct pattern: they were arranged in a circle with a diameter of about 5 feet. what i had stumbled upon were the gnarled remains of an enormous ancient tree stump. all that was left were vestiges of the outermost edge. the interior had completely rotted into humus long ago—a clear indication that the tree must have been felled at least four or five hundred years earlier. but how could the remains have clung onto life for so long?
part a
this sentence is from the passage.
\scientists investigating similar situations have discovered that assistance may either be delivered remotely by fungal networks around the root tips—which facilitate nutrient exchange between trees—or the roots themselves may be interconnected.\
what does the phrase facilitate nutrient exchange mean as it is used in the sentence?

1. enable nutrients to be exchanged
2. prepare nutrients to be exchanged
3. control how nutrients are exchanged
4. determine how nutrients are exchanged

Explanation:

The phrase "facilitate nutrient exchange" means to make the exchange of nutrients between trees possible or enable this process. Looking at the context, the fungal networks help nutrients be exchanged between interconnected trees, so the phrase refers to enabling this nutrient transfer.

Answer:

1. enable nutrients to be exchanged