This question assesses the ability to translate English into Chinese accurately, focusing on the correct use of terms related to cultural heritage. - A. 'The Opera House has been included in the list of cultural heritage sites' is the most accurate and formal translation. - B. 'The Opera House is included in the list of cultural heritage sites' is slightly less formal and less accurate. - C. 'The Opera House is considered part of cultural heritage' is somewhat vague and not as precise as option A. - D. 'The Opera House is added to the list of cultural heritage sites' is slightly informal and less accurate in terms of cultural heritage. The correct answer is A. 歌剧院已经被列入文化遗产名单, as it provides the most accurate and formal translation for the context of cultural heritage sites.