Question: What sport are Mary-Ann Eisel and Christo van Rensburg known for playing?

full_context: Document 1: Arthur Ashe: Arthur Robert Ashe Jr. (July 10, 1943 – February 6, 1993) was an American professional tennis player. He won three Grand Slam titles.
Document 2: Linky Boshoff: Delina Ann Boshoff-Mortlock, commonly known as Linky Boshoff, (born 12 November 1956), is a former professional tennis player who won the 1976 US Open women's doubles title with her partner Ilana Kloss.
Document 3: Johan Kriek: Johan Kriek (born April 5, 1958) is a South African-American professional male tennis player and founder of the Global Water Foundation, a non-profit organization dedicated to delivering clean water to the world's neediest communities. Kriek won two Australian Opens and reached the semifinals at the French Open and US Open, as well as the quarterfinals of Wimbledon. He won 14 professional singles and 8 doubles titles, reaching a career-high singles ranking of World No. 7. Kriek's most memorable wins include victories over Andre Agassi, Jimmy Connors, John McEnroe, Guillermo Vilas, Stefan Edberg, Michael Chang, Vitas Gerulaitis and Björn Borg.
Document 4: Roscoe Tanner: Roscoe Tanner (born October 15, 1951) is a retired American professional tennis player, who turned pro in 1972 and reached a career-high world singles ranking of World No. 4 on July 30, 1979.
Document 5: Tony Roche: Anthony Dalton Roche, AO MBE (born 17 May 1945) is a former professional Australian tennis player, native of Tarcutta. He played junior tennis in the New South Wales regional city of Wagga Wagga. He won one Grand Slam singles title and thirteen Grand Slam doubles titles, and was ranked as high as World No. 2 by Lance Tingay of "The Daily Telegraph" in 1969. He also coached multi-Grand Slam winning World No. 1s, Ivan Lendl, Patrick Rafter, Roger Federer, Lleyton Hewitt and former World No. 4, Jelena Dokic.
Document 6: Kevin Curren: Kevin Melvyn Curren (born 2 March 1958) is a South African-American former professional tennis player. He played in two Grand Slam singles finals and won four Grand Slam doubles titles, reaching a career-high singles ranking of World No. 5.
Document 7: Marc Rosset: Marc Rosset (born 7 November 1970) is a former professional tennis player from Switzerland who is best remembered for winning the men's singles gold medal at the 1992 Olympic Games. He also won one Grand Slam doubles title at the French Open in 1992 partnering compatriot Jakob Hlasek.
Document 8: Mary Joe Fernández: Mary Joe Fernández Godsick (born María José Fernández; August 19, 1971) is an American former professional tennis player. She reached a career-high ranking of world No. 4 in both singles and doubles. Fernández was the runner-up in three Grand Slam singles tournaments and won two Grand Slam women's doubles titles and two Olympic gold medals.
Document 9: Tracy Austin: Tracy Ann Austin Holt (born December 12, 1962) is an American former World No. 1 retired professional tennis player. She won three Grand Slam titles, including the women's singles titles at the 1979 and 1981 US Opens, and the mixed doubles title at the Wimbledon Championships in 1980. Additionally, she won the WTA Tour Championships in 1980 and the year-ending Toyota Championships in 1981, both in singles. A series of injuries and a serious automobile accident cut short her career. Since 1979, she has been the youngest US Open female singles champion in history, and she is the youngest inductee of all time at the International Tennis Hall of Fame. Austin won singles titles on all playing surfaces: clay (both red clay and green clay), indoor carpet, grass, and hard courts.
Document 10: Mona Guerrant: Anne Guerrant, also known as Mona Anne Guerrant, was an American professional tennis player from 1971–1980. She ranked as high as #11 in the world in singles in 1976 and was the winner of four singles titles in Portland, South Florida, and in Wellington and Auckland, New Zealand. She won many doubles titles on the pro tour with several different partners including Ann Kiyomura and Kerry Reid with whom she won the Australian Open doubles title in 1977. She was a women's doubles and mixed doubles standout in World Team Tennis and was part of the #1 women's doubles team in the League with Billie Jean King in 1975 and the #1 mixed doubles team with Ross Case in 1978. Anne retired from the pro tour in 1980, and since then she has also won one world and fourteen age group National Singles Championships as of 2016. She is a retired real estate entrepreneur, a philanthropist, and author of "How to Be Richer Than Your Parents," a book about finances for high schoolers and young adults.
Document 11: 1985 US Open – Mixed Doubles: Manuela Maleeva and Tom Gullikson were the defending champions but lost in the second round to Kathleen Horvath and Leif Shiras.
Document 12: Mary-Ann Eisel: Mary–Ann Eisel (born November 25, 1946) is an American former tennis player. She was the US Open mixed doubles champion in 1968.
Document 13: 1984 US Open – Mixed Doubles: Elizabeth Sayers and John Fitzgerald were the defending champions but lost in the final 2–6, 7–5, 6–4 against Manuela Maleeva and Tom Gullikson.
Document 14: 1968 US Open (tennis): The 1968 US Open (formerly known as U.S. National Championships) was a tennis tournament that took place on the outdoor grass courts at the West Side Tennis Club, Forest Hills in New York, United States. The tournament ran from 29 August until 8 September. It was the 88th staging of the tournament and the fourth Grand Slam event of 1968. It was the first edition of the tournament in the Open Era of tennis and as such for the first time offered prize money, totaling $100,000. Arthur Ashe and Virginia Wade won the singles titles. Ashe was still registered as an amateur and therefore not entitled to the $14,000 first-prize money, which instead went to runner-up Tom Okker, while Wade earned $6,000. Frank Parker, at the age of 52, lost to eventual champion Arthur Ashe in the second round, and still holds the record for the oldest man to compete in a Grand Slam singles tournament.
Document 15: Christo van Rensburg: Christo van Rensburg (born 23 October 1962) is a former professional tennis player from South Africa.
ground_truth: tennis player