Read this sentence: when the scientists drilled into the ground, they found a system of subterranean rivers. based on the context, subterranean means which of the following?

Subterranean means "under the ground", the context helps us know this. As the scientists drilled into the ground, it is obvious that they were searching for something under or below it.

Also by reading the word "subterranean" we can notice a prefix, which is sub-. This prefix means "bellow or under something". Added to the root word terra which means "earth".

choice 2 i like that prompt better.