The correct answer is A. There
Explanation:
Generally speaking, capitalization should be used for proper nouns such as names of people, companies, places, etc.; in the case of titles of books, artistic works, plays, etc and with no exception in the first word in a text, paragraph or the word after a period (.). This means in the sentence "there is one thing every visitor should know: the city is divided into five regions, and each has many educational and cultural attractions" the word "there" should be capitalized as even if this is not a proper noun or similar is the first word in the sentence and thus, the option that corrects the capitalization mistake is "There".
