Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions.

Born on June 30, 1985 in Baltimore, Maryland, to Fred and Debbie Phelps, the youngest of three children, Michael Phelps and his sisters grew up in the neighbourhood of Rodger Forge. His father, Fred, a former all-rounded athlete, was a state trooper and his mother Debbie was a middle-school principal. When Phelps's parents divorced in 1994, he and his siblings lived with their mother, with whom Michael grew very close. Even at the age of 7, Phelps was still a little scared to put his head under water, so his instructors allowed him to float around on his back. Not surprisingly, despite the fact that later he is very good at butterfly swimming, the first stroke he mastered was not the easily-practised breaststroke but the backstroke. At the age of 15, Phelps became the youngest American male swimmer to compete at an Olympic Games in 68 years. While he didn't win any medals at the 2000 Summer Olympics in Sydney, Australia, he would soon become a major force in competitive swimming. In the spring of 2001, Phelps set the world record in the 200-meter butterfly, becoming the youngest male swimmer in history at the age of 15 years and 9 months. At the 2001 World Championships in Japan, he then broke his own record with a time of 1:54:58, earning his first international medal. In 2002, Phelps continued to establish several records including the 100- meter butterfly and the 200-meter individual medley. The following year, at the same event, he broke his own world record in the 400-meter individual medley with a time of 4:09.09. After the London Olympics in 2012, Phelps announced he was retiring from his sport. However, at the 2016 Olympic Games, he came out of retirement and returned to professional competition. This was also the event in which he won one silver and five gold medals, becoming the oldest individual gold medalist in Olympic swimming history, as well as the first swimmer to win four consecutive golds in the same event, the 200 meter individual medley.

Mark the letter A, B, C or D to indicate the word that differs from the other three A. initiative B. necessary