Robin recently bought voice over internet protocol (voip) phone service. a few of robin's friends bought voip before she did, but many other friends were interested in robin's opinions of the new phone service. robin is a(n) in this product category.

For this particular case and scenario, Robin is actin in the role of an early adopter. So, the correct word to fill in the blank will be "early adopter".

Explanation:

An early adopter is a consumer of a specifical product or service who acquires the service before others and provides useful feedback to companies. In this way, a company can rely on a person in order to refine future releases and improve their processes.

a is the answer because it just is

i r r e l e v a n t