Final answer:
Keith will be assuming the role of a responder when he provides information to the Environmental Agency inspector as requested.
Step-by-step explanation:
When Keith gets back to the Environmental Agency (EA) inspector with the information the inspector requested, Keith will be assuming the role of a responder. In this context, a responder is someone who replies or provides information when it is asked for, especially in an official capacity. Being an informant generally suggests providing secret or confidential information, and an assistant implies a larger role in helping to carry out tasks. A collaborator typically works together with others on the same task or project, which doesn't seem to be the scenario described here. Since Keith is supplying the requested information to the EA inspector, he best fits the role of a responder.