Donna sometimes gets overwhelmed even thinking about research on human development, because there is so much data out there to consider. She is grateful that others have developed theories, because it helps her to determine which data is:.

Relevant.

Explanation:

As the exercise suggests with the example, what Donna is so grateful of is to be able to determine which data is relevant; what often happens to investigators, teachers or students is that, when researching on particular topics, much information is found. Many times we are overwhelmed by the amount and it is very helpful to find critics, thinkers, disseminators that helps us determine which is relevant, helpful, from what it's not.

50% i think

explanation:

permafrost layer, it exists beneath a layer of soil, rock or sediment.