Question: What was the nationality of the defending champion at the Men's Singles tournament of the 2013 BWF World Championships?

Context paragraphs:
Lee Chong Wei career statistics: This is a list of the main career statistics of Malaysian professional badminton player, Lee Chong Wei.  To date, Lee has won sixty three singles titles, including eleven Super Series Premier titles, twenty-eight Super Series titles, and four Super Series Finals titles.  He is the first men's singles player to win at least once in different Super Series Premier titles.  He is also a Silver medalist at the 2008 Summer Olympics, 2012 Summer Olympics and the 2016 Summer Olympics.  He is the runner-up at the 2011 BWF World Championships, 2013 BWF World Championships and 2015 BWF World Championships.  His achievement as the runner-up at the 2014 BWF World Championships was canceled due to doping violations.  Following that matter, he served an 8-month suspension from international competitions.

2013 BWF World Championships – Women's singles: The Women's Singles tournament of the 2013 BWF World Championships was held from August 5–11.  Wang Yihan was the defending champion.  Ratchanok Inthanon defeated Li Xuerui 22–20, 18–21, 21–14 in the final.

2013 BWF Season: The 2013 BWF Season was the overall badminton circuit organized by the Badminton World Federation (BWF) for the 2013 badminton season to publish and promote the sport.  Besides the BWF World Championships, BWF promotes the sport of Badminton through an extensive worldwide programme of events in four structure levels.  They were the individual tournaments called Super Series, Grand Prix Events, International Challenge and International Series.  Besides the individual tournaments, Team Events such as Thomas Cup & Uber Cup and Sudirman Cup are held every other year.

2011 BWF World Championships – Men's singles: The Men's Singles tournament of the 2011 BWF World Championships was held from August 8–14.  Chen Jin was the defending champion.

2012 BWF World Junior Championships – Teams event: The Team event tournament of the 2012 BWF World Junior Championships was the fourteenth tournament of the BWF World Junior Championships.  It was held from October 25–28, 2012 in Chiba, Japan.  According to the Badminton World Federation (BWF) 30 teams have confirmed their participation.  The winner of the tournament would have Suhandinata Cup for about a year until the next BWF World Junior Championships Team Event is held.

2014 BWF World Junior Championships – Teams event: The Team event tournament of the 2014 BWF World Junior Championships was the sixteenth tournament of the BWF World Junior Championships.  It was held from April 7–11, 2014 in Alor Setar, Malaysia.  According to the Badminton World Federation (BWF) 35 teams have confirmed their participation.  The winner of the tournament would have Suhandinata Cup for about a year until the next BWF World Junior Championships Team Event is held.

2013 BWF World Junior Championships – Teams event: The Team event tournament of the 2013 BWF World Junior Championships was the fifteenth tournament of the BWF World Junior Championships.  It was held from October 23–27, 2013 in Bangkok, Thailand.  According to the Badminton World Federation (BWF) 32 teams have confirmed their participation.  The winner of the tournament would have Suhandinata Cup for about a year until the next BWF World Junior Championships Team Event is held.

2011 BWF World Championships – Women's singles: The Women's Singles tournament of the 2011 BWF World Championships was held from August 8–14.  Wang Lin was the defending champion.

2013 BWF World Championships – Men's singles: The Men's Singles tournament of the 2013 BWF World Championships was held from August 5–11.  Lin Dan was the defending champion.

Lin Dan: Lin Dan (born October 14, 1983) is a Chinese professional badminton player.  He is a two-time Olympic champion, five-time World champion, as well as a six-time All England champion.

Supporting paragraphs: 2013 BWF World Championships – Men's singles Lin Dan
Answer: Chinese