Answer: The tense of the verb "had visited" is C) past perfect.
Explanation: The Past Perfect Tense is used to refer to an past event or situation that took place and was completed before another past action. This tense gives writers/speakers the possibility of showing a clear sequence of events. Moreover, the Past Perfect Tense is formed with the past tense of the verb "have", which is "had", and the past participle of the main verb. The tense of "had visited" is Past Perfect because it has been formed with "had" + the past participle of the verb "visit", which is "visited".