Question: What sport do Lucie Šafářová and Danie Visser play?
Context: Kristina Mladenovic and Lucie Šafářová were the defending champions, but Mladenovic chose not to participate this year.  Šafářová played alongside Květa Peschke, but they lost in the first round to Chan Hao-ching and Chan Yung-jan. Bethanie Mattek-Sands and Lucie Šafářová were the defending champions, but Mattek-Sands was unable to compete due to injury.  Šafářová played alongside Barbora Strýcová, but lost in the semifinals to Lucie Hradecká and Kateřina Siniaková. Danie Visser (born 26 July 1961) is a former professional tennis player from South Africa.  A doubles specialist, he won 3 Grand Slam men's doubles titles (2 Australian Open and 1 US Open).  Visser reached the World No. 1 doubles ranking in January 1990. This list summarizes the main career statistics of Czech professional tennis player Lucie Šafářová.  To date, Šafářová has won seven WTA singles titles and fifteen WTA doubles titles including five Grand Slam doubles titles with Bethanie Mattek-Sands at the 2015 Australian Open and French Open,; the 2016 US Open and 2017 Australian Open and French Open.  Other highlights of Šafářová's career thus far include winning the 2015 Qatar Total Open, reaching the final of the 2015 French Open and making quarterfinal and semifinal appearances at the 2007 Australian Open and 2014 Wimbledon Championships, respectively.  Šafářová achieved career high singles and doubles rankings of World No. 5 and World No. 2 on 14 September 2015 and 30 January 2017. Lucie Šafářová (] ; born 4 February 1987) is a Czech professional tennis player from Brno.  She is currently the WTA world No. 1 doubles player.  Šafářová has won seven WTA tour singles titles, fifteen doubles titles and reached the quarterfinals of the 2007 Australian Open by upsetting defending champion Amélie Mauresmo in the fourth round.  She reached her first Grand Slam semifinal at the 2014 Wimbledon Championships and her first Grand Slam final at the 2015 French Open.  She also won the 2015 Australian Open, 2015 French Open, 2016 US Open, 2017 Australian Open and 2017 French Open women's doubles titles partnering with Bethanie Mattek-Sands. Bethanie Mattek-Sands and Lucie Šafářová were the defending champions, but Mattek-Sands chose not to participate this year.  Šafářová played alongside Sabine Lisicki, but lost in the semifinals to Martina Hingis and Sania Mirza. <br> Eddie Edwards and Danie Visser were the defending champions, but Edwards did not participate this year.  Visser partnered Christo Steyn. Bethanie Mattek-Sands and Lucie Šafářová were the defending champions, but decided not to compete together.  Mattek-Sands played alongside Heather Watson, but lost in the quarterfinals to Andreja Klepač and Katarina Srebotnik.  Šafářová teamed up with Tímea Babos, but lost in the first round to Kateryna Bondarenko and Olga Savchuk. Danie Visser and Laurie Warder were the defending champions, but they did not compete together this year.  Visser participated alongside Jim Grabb and was defeated in the first round by Sergio Casal and Emilio Sánchez, while Warder participated alongside Brett Steven and was defeated also in the first round by Goran Ivanišević and Marc Rosset. Rick Leach and Danie Visser were the defending champions, but did not partner together this year.  Leach partnered Jared Palmer, losing in the semifinals.  Visser partnered Patrick Galbraith, losing in the final.
Answer: tennis