Question: Mary Pierce and Shelby Cannon, share which occupation?

Context paragraphs:
2000 du Maurier Open – Women's Doubles: The 2000 du Maurier Open – Women's Doubles was the women's doubles event of the one hundred and eleventh edition of the Canadian Open; a WTA Tier I tournament and the most prestigious women's tennis tournament held in Canada.  Jana Novotná and Mary Pierce were the defending champions, but Novotná retired from professional tennis in 1999 and Pierce did not compete at the tournament.  Martina Hingis and Nathalie Tauziat won the title by defeating Julie Halard-Decugis and Ai Sugiyama 6–3, 3–6, 6–4 in the final.  It was the 11th title for Hingis and the 21st title for Tauziat in their respective doubles careers.

1993 Qatar Open – Doubles: Boris Becker and Patrik Kühnen won the title, defeating Shelby Cannon and Scott Melville 6–2, 6–4 in the final.

1990 US Open – Mixed Doubles: Robin White and Shelby Cannon were the defending champions but lost in the second round to Zina Garrison and Rick Leach.

2004 JPMorgan Chase Open – Doubles: Mary Pierce and Rennae Stubbs were the defending champions, but had different outcomes.  While Pierce did not compete this year, Stubbs partnered with Cara Black, but they lost in first round to Daniela Hantuchová and Chanda Rubin.

Mary Pierce: Mary Pierce (born 15 January 1975) is a French retired tennis professional who played on the Women's Tennis Association (WTA) tour.  Born in Canada, she is a citizen of Canada, and the United States.  Pierce played for France in team competitions and in the Olympics.

1999 Kremlin Cup – Women's Doubles: The 1999 Kremlin Cup – Women's Doubles was the women's doubles event of the fourth WTA edition of the Kremlin Cup; a WTA Tier I tournament and the most prestigious tournament held in Russia.  Mary Pierce and Natasha Zvereva were the defending champions, but Pierce competed this year with Barbara Schett, whereas Zvereva competed with Elena Tatarkova.

1996 EA-Generali Open – Doubles: Francisco Montana and Greg Van Emburgh were the defending champions but they competed with different partners that year, Montana with Donald Johnson and Van Emburgh with Shelby Cannon.

1999 Australian Open – Women's Doubles: The 1999 Australian Open – Women's Doubles was the women's dobules event of the eighty-seventh edition of the Australian Open, the first Grand Slam of the year and the most prestigious tournament in the Asia-Pacific and the Southern Hemisphere.  Martina Hingis and Mirjana Lučić were the defending champions, but Hingis competed with Russian Anna Kournikova, and Lučić competed with Frenchwoman Mary Pierce.  Lučić and Pierce were defeated in the first round by Christina Singer and Helena Vildová. <br>

Shelby Cannon: Shelby Cannon (born August 19, 1966, in Hattiesburg, Mississippi) is an American retired professional tennis player.

Sandrine Testud: Testud broke into top 20 singles rankings in July 1997.  On February 7, 2000, she became the sixth Frenchwoman after Françoise Dürr, Mary Pierce, Nathalie Tauziat, Amélie Mauresmo and Julie Halard to break into the singles top 10 rankings.  This marked the first time France had four women ranked in the singles Top 10 simultaneously (Mary Pierce at No. 5, Nathalie Tauziat at No. 6, Julie Halard at no.8 and Testud at No. 9).  France was the third nation after the USA and Australia to have more than two representatives in the singles Top 10 at any one time.  She finished in the top 20 singles rankings for five consecutive years between 1997 and 2001.  In the summer of 2002, she took a break from the tennis circuit when she discovered that she was pregnant with her first child.  She resumed her career 12 months after the birth of her child and retired in the summer of 2005.

Supporting paragraphs: Mary Pierce Shelby Cannon
Answer: tennis professional