Frederick, an environmental major, delivered a speech to a large subdivision on how to cut down on pollution. When he had completed his speech, several people came forward and told him they found this information useful. Frederick has attained what type of credibility:

Frederick has attained a Terminal Credibility.

Explanation:

Credibility means to be trustworthy. It relates to the perception the Audience have for the speaker. If the audience can trust the speaker, then they can believe the speaker whereas when the speaker has poor reputation  or does not appear to be trustworthy, then the audience will be less likely to listen to him as he speaks.

Terminal Credibility is a type of a credibility where the speaker has either gained or lost after delivering a speech. it is like the lasting impression that the audience has for the speaker. in the case of Frederick, He attained Terminal credibility since the audience came forward after he had completed his speech and told him they found his speech useful. It is terminal credibility because it was when he had completed his speech that the audience came forward to give their opinion. not during the speech  like in derived credibility nor before the speech like in initial credibility.