The correct answer is: A. 1541.
The Church of Our Lady, also known as the Church of the Assumption of the Blessed Virgin Mary, is a Roman Catholic church in the city of Tallinn, Estonia. It is the oldest church in Tallinn and one of the oldest churches in Estonia. The church was built in the Gothic style and was completed in 1541. It is a popular tourist destination and is considered to be one of the most important landmarks in Tallinn.
Option B is incorrect because the Church of Our Lady was completed in 1541, not 1620.
Option C is incorrect because the Church of Our Lady was completed in 1541, not 1521.
Option D is incorrect because the Church of Our Lady was completed in 1541, not 1687.