challenge: What is a notable achievement of Romanian biathlete George Buta?
  
  A. He won a silver medal at the 2018 Winter Olympics
  B. He won the gold medal in super-sprint at the Summer Biathlon World Championships 2021
  C. He won the bronze medal in the 2019 Biathlon World Championships
  D. He competed in the 2020 Summer Olympics
  Answer: 