The correct answer is: The Bastille Prison, where many important people were at one time imprisoned, is today visited by tourists.
The Bastille was a prison in Paris, France, that was stormed by revolutionaries on July 14, 1789, an event that is considered to be the start of the French Revolution. The prison was demolished in 1791, but the site is now a popular tourist destination.
The verb “to be” can be used in a variety of tenses, including the past tense, present tense, and future tense. In this case, the past tense is used because the Bastille was a prison in the past and is no longer in use. The present tense is used because the site of the Bastille is a tourist destination today.
The other options are incorrect because they do not agree with the tense of the sentence. The verb “to have been” is used in the past perfect tense, which is used to talk about something that happened before another event in the past. The verb “to had been” is used in the past perfect progressive tense, which is used to talk about something that was happening before another event in the past. The verb “were” is used in the past tense, but it does not agree with the tense of the sentence. The verb “is” is used in the present tense, but it does not agree with the tense of the sentence. The verb “will be” is used in the future tense, but it does not agree with the tense of the sentence.