Answer:
Rick and Rachael have been dating ever since they met.
Explanation:
Subject-Verb Agreement: The subject "Rick and Rachael" is plural because it refers to two people. Therefore, the verb should be plural as well. "Has" is singular; the correct form for plural subjects is "have".
In the context of the sentence, "been" is used to indicate that the action of dating started in the past and has continued up to the present moment. The phrase "have been dating" is in the present perfect continuous tense. This tense is used to express an action that started in the past, is still ongoing, and may continue into the future.
