Which player completed the Golden Slam, all four Majors and the Olympic singles gold in the same year, in 1988?

The correct answer is B, Steffi Graf. In 1988 the German won the Australian Open, the French Open, Wimbledon and the US Open, and then took the Olympic singles gold medal at Seoul, the first Games at which tennis was again a full medal sport. No other player, man or woman, has completed all five in a single year.

Option A, Martina Navratilova, won eighteen Major singles titles including nine at Wimbledon, and held all four at once across two seasons, but never inside one calendar year and never with an Olympic gold. Option C, Margaret Court, completed the calendar Grand Slam in 1970 and holds the all-time record of twenty-four women's singles Majors, but tennis was not then an Olympic medal sport. Option D, Serena Williams, holds the Open Era women's record of twenty-three Major singles titles and has Olympic gold medals, but her four in a row, the so-called Serena Slam, ran across 2014 and 2015 rather than one year.