Question: Who was ranked World No. 1 in double first, Robert Seguso or Tom Okker?

Context paragraphs:
Milan Šrejber: Milan Šrejber (] ) (born 30 December 1963) is a former tennis player from Czechoslovakia, who represented his native country at the 1988 Summer Olympics in Seoul.  There he reached the semi finals of the men's doubles competition, partnering Miloslav Mečíř.  The pair was defeated by America's eventual winners Ken Flach and Robert Seguso, but still won the bronze medal.  The right-hander won one career singles title (Rye Brook, 1988), and reached his highest ATP singles ranking of World No. 23 in October 1986.

Frew McMillan: Frew Donald McMillan (born 20 May 1942) is a former professional male tennis player from South Africa who won five major doubles championships including three Wimbledons with Bob Hewitt.  Altogether, he won 63 doubles titles, surpassed only by the Bryan brothers, Todd Woodbridge, John McEnroe and Tom Okker.  He was also ranked No.1 in Doubles on the ATP Computer for a significant period from 1977 to 1979 when he was aged 37.

Robert Seguso: Robert Arthur Seguso (born May 1, 1963) is a former professional tennis player from the United States.  A doubles specialist, he won four Grand Slam men's doubles titles (two Wimbledon, one French Open and one US Open).  He also won the men's doubles Gold Medal at the 1988 Olympic Games in Seoul, partnering Ken Flach.  Seguso reached the World No. 1 doubles ranking in 1985.  He won a total of 29 career doubles titles between 1984 and 1991.

Nduka Odizor: Nduka Odizor (born 9 August 1958) is a former tennis player from Nigeria, who represented his native country at the 1988 Summer Olympics in Seoul, where he was defeated in the first round by American lucky loser Robert Seguso.  The right-hander won one career title in singles (Taipei, 1983) and seven doubles titles.  He reached his highest ATP singles ranking of World No. 52 in June 1984.

1987 US Open – Men's Doubles: The Men's Doubles tournament at the 1987 US Open was held from September 1 to September 14, 1987, on the outdoor hard courts at the USTA National Tennis Center in New York City, United States.  Stefan Edberg and Anders Järryd won the title, defeating Ken Flach and Robert Seguso in the final.

Ken Flach: Kenneth Eliot Flach (born May 24, 1963) is a former professional tennis player from the United States.  A doubles specialist, he won 4 Grand Slam men's doubles titles (2 Wimbledon and 2 US Open), and 2 Grand Slam mixed doubles titles (1 Wimbledon and 1 French Open).  He also won the men's doubles Gold Medal at the 1988 Olympic Games in Seoul, partnering Robert Seguso.  Flach reached the World No. 1 doubles ranking in 1985.

1973 WCT World Doubles – Doubles: This was the first edition of the WCT World Doubles tennis tournament.  The eight highest ranking teams qualified for the event.  Third seeds, Robert Lutz and Stan Smith won the tournament in straight sets in the final against Tom Okker and Marty Riessen

1987 Wimbledon Championships – Men's Doubles: Ken Flach and Robert Seguso defeated Sergio Casal and Emilio Sánchez 3-6, 6-7(6), 7-6(3), 6-1, 6-4 in the final to win the Gentlemen's Doubles title at the 1987 Wimbledon Championships.

Tom Okker: Thomas Samuel Okker (born 22 February 1944) is a former Dutch tennis player.  He was ranked among the world's top 10 singles players for seven consecutive years, 1968–74, reaching a career high of World No. 3 in 1969.  He also was ranked World No. 1 in doubles in 1969.

1986 Tokyo Indoor – Doubles: Ken Flach and Robert Seguso were the defending champions, but Seguso did not participate this year.  Flach partnered Paul Annacone, losing in the first round.

Supporting paragraphs: Robert Seguso Tom Okker
Answer: Thomas Samuel Okker