Question

read the passage and then answer the question.
although plants dont talk, they do communicate with each other by sending messages. for example, scientists have found that some trees can communicate to share resources like water. they do this by sending messages through an underground network. a certain kind of fungus connects all the trees in the forest together, forming a large network. scientists believe this information - sharing web may allow larger, older trees to help younger trees survive. this improves the health of the entire forest. the details of how the communication works are still obscure, so further research is needed to better understand the process.
what is the meaning of obscure as used in the passage?
not clearly understood
well established
highly unusual
scientific

Explanation:

To determine the meaning of "obscure" in the passage, we analyze the context. The sentence says "the details of how the communication works are still obscure, so further research is needed to better understand the process." The need for further research implies that the details are not fully or clearly understood yet. "Well established" would mean the details are clear and confirmed, which contradicts the need for research. "Highly unusual" refers to something being out of the ordinary, which doesn't relate to the clarity of understanding. "Scientific" is about the method or field, not the clarity of details. So "not clearly understood" matches the context.

Answer:

A. not clearly understood