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

full_context: Document 1: 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.
Document 2: Lee Chong Wei: Dato' Lee Chong Wei {'1': ", '2': ", '3': 'DSPN DB DCSM PJN', '4': "} (born 21 October 1982) is a Malaysian professional badminton player. As a singles player, Lee was ranked first worldwide for 199 consecutive weeks from 21 August 2008 to 14 June 2012. He is the fourth Malaysian player after Rashid Sidek, Roslin Hashim and Wong Choong Hann to achieve such a ranking (since official rankings were first kept in the 1980s), and is the only Malaysian shuttler to hold the number one ranking for more than a year.
Document 3: Carolina Marín: Carolina María Marín Martín (born 15 June 1993) is a professional badminton player from Spain. She is the Olympic Champion, two time World Champion, three time European Champion and the former World No.1 in BWF rankings for the badminton women's singles. Carolina Marin is currently ranked No. 4 in the World by Badminton World Federation. She became the World Champion in women's singles two times in a row in 2014 and 2015. She won her first Olympics gold medal in women's singles at the 2016 Rio Olympics after defeating P. V. Sindhu of India.
Document 4: P. V. Sindhu: Pusarla Venkata Sindhu (born 5 July 1995) is an Indian professional badminton player, who is currently world no 2 in the BWF World Ranking. At the 2016 Summer Olympics, she became the first Indian woman to win an Olympic silver medal. She is one of the two Indian badminton players to ever win an Olympic medal – other being Saina Nehwal. She was also a silver medalist at the 2017 BWF World Championships and, in 2017, became first Indian ever to win Korea Open Super Series.
Document 5: 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.
Document 6: 2013 Men's Asian Individual Squash Championships: The 2013 Men's Asian Individual Squash Championships is the men's edition of the 2013 Asian Individual Squash Championships, which serves as the individual Asian championship for squash players. The event took place in Islamabad in Pakistan from 1 to 5 May 2013. Aamir Atlas Khan won his first Asian Individual Championships title, defeating Abdullah Al Muzayen in the final.
Document 7: Saina Nehwal: Saina Nehwal (   ; born 17 March 1990) is an Indian professional badminton singles player. She is one of the greatest players of her time. Nehwal, the former world no. 1 has won over twenty one international titles, which include ten Superseries titles. Although she reached to the world no. 2 ranking in 2009, it was only in 2015 that she was able to attain the world no. 1 ranking. And thereby becoming the only female player from India and overall the second Indian player – after Prakash Padukone – to achieve this feat. She has represented India three times in the Olympics, winning bronze medal in her second appearance.
Document 8: 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.
Document 9: Liliyana Natsir: Liliyana Natsir (born 9 September 1985) is an Indonesian female badminton player who specializes in doubles. With one gold and silver from Olympic Games and four gold medals at BWF World Championships, she is regarded as one of the greatest mixed doubles players in the history. She gained huge success by partnering with two different players. Her current partner is Tontowi Ahmad since 2011, after separating from her previous partner, Nova Widianto. She also won three titles in a row from 2012–2014 at All England Badminton Championships, one of the most prestigious and oldest tournament in the sport. Been entering the top level since 18 years old, her tactical awareness, game vision, and dominance at the front court are considered as one of the best in the tour. In 2016, she and Tontowi Ahmad became the first Indonesian mixed doubles pair to win gold medal at the Olympic Games by beating Chan Peng Soon and Goh Liu Ying of Malaysia.
Document 10: 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.
Document 11: Lee–Lin rivalry: The Lee–Lin rivalry is between two legendary badminton players, Datuk Wira Lee Chong Wei of Malaysia and Lin Dan of China. The rivalry is considered to be one of, if not, the greatest rivalry in badminton history. More often than not, the dominance of the two legendary shuttlers have been compared to that of tennis greats Roger Federer and Rafael Nadal in tennis. They have played a total of 38 times, and Lin Dan leads their rivalry 26–12. Lee Chong Wei and Lin Dan are by far the two of the most dominant players across three generations and many regard Lin Dan and Lee Chong Wei as the 2 greatest badminton players of all time. In their homeland, each hold a military rank, with Lee a Commander (Honorary) of the Royal Malaysian Navy Volunteer Reserve Unit and Lin a retired Lieutenant-Colonel in the People's Liberation Army having being promoted from the ranks of Lieutenant-Commander and Major respectively, meaning they have the same seniority in terms of military rank. They have contested in many major tournament finals and are currently the only two badminton singles players who have contested in two Olympic finals where Lin Dan won both of the time. They have also contested two BWF World Championships finals and one Asian Games final where all matches were very close hard fought 3 setters and won by Lin Dan. There 2011 World Badminton Championship match widely touted as one of the greatest badminton matches of all the time. In the semi-finals of the 2016 Rio Olympics, most possibly the last Olympic Games of both athletes' careers, Lee Chong Wei won against Lin Dan, for the first time on the Olympic stage, making Lee the second shuttler in any discipline of the sport in history to reach 3 consecutive finals after Fu Haifeng who had achieved the feat a few hours earlier in the men doubles. The two players exchanged a special moment in their rivalry and exchanged shirts as they exited the court. The 2016 Rio Games marks an end in the badminton era dominated by Lee and Lin. Nevertheless, the pair are good friends off court, having invited one another to each other's wedding and sharing a mutual love for fast cars and watches. Among the cars that Lee owns include a crystal grey Bentley Continental GT, a white Audi R8, a white Ferrari F430, a grey Nissan Skyline GTR, Range Rover Evoque, yellow Lamborghini Aventador and a BMW X6 besides the cars given to him by national automaker Proton. Lin, on the other hand, has a Porsche Panamera, a grey Aston Martin DBS and also a black Nissan Skyline GTR among his vast collection of supercars.
Document 12: 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.
Document 13: 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.
Document 14: 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.
Document 15: Zhao Yunlei: Zhao Yunlei (born August 25, 1986) is a mixed and women's doubles badminton athlete from China. She graduated with a BA from Huazhong University of Science and Technology. She is the first and only badminton player to have ever won two Gold medals in the same Olympic edition, winning in both the Mixed and Women's Doubles categories in 2012. Zhao joins the ranks with nine other players with two Olympic Gold Medals, the highest number of Gold Medals won by any badminton athlete. Through her performance at the 2014 and 2015 BWF World Championships, she became the first player to win two consecutive gold medals in two consecutive BWF World Championships.
ground_truth: Chinese