Final answer:
The minimum age requirement for the Triwizard Tournament is 17 years old to ensure participants can handle the dangerous challenges.
Step-by-step explanation:
The minimum age required to participate in the Triwizard Tournament is D) 17. This age restriction was put in place to ensure that only the most skilled and mature students from each participating school are allowed to take on the dangerous challenges the tournament presents. Originally, there was no age limit, but after the events of the 1994-1995 tournament, as depicted in Harry Potter and the Goblet of Fire, a minimum age of 17 was instituted as an additional safety measure.