The correct answer is option 2, Queen Elizabeth II. Queen Elizabeth II is the current British monarch and she is the longest-reigning queen regnant in British history. She ascended to the throne on February 6, 1952, following the death of her father, King George VI. As of 2021, she has been on the throne for over 69 years.

Option 1, Queen Victoria, was indeed one of the longest-reigning British monarchs, serving from 1837 to 1901. However, Queen Elizabeth II has surpassed her in terms of years on the throne.

Option 3, Queen Mary Tudor, also known as Mary I, ruled from 1553 until her death in 1558.

Option 4, Queen Anne, reigned from 1702 to 1714 and was the last monarch of the Stuart dynasty.

Queen Elizabeth II holds the record as the oldest British monarch to sit on the throne, and she continues to fulfill her duties as queen.