Question: Which central defender spent 20 years of his career at Arsenal F.C. Academy?

Context paragraphs:
Jock Adie: Jock Adie (born 2 March 1930 in Windygates, Fife) is a Scottish former footballer who played as a left-back.  Adie began his career in the late 1940s with Heart of Midlothian, spending seven years with the Tynecastle side before moving back to Fife with East Fife.  The defender spent three years at Bayview Park before having a short spell in 1958 with Dundee United, making his debut in August of that year.  A couple of months later, Adie lost his first-team place and appears to have been released shortly after; it is unknown where his career headed after his time at Tannadice.

William Goodell (missionary): William Goodell (1792–1867) was an American missionary.  He was born at Templeton, Mass., educated at Phillips Academy (Andover), Dartmouth College, and Andover Theological Seminary.  He was accepted as a missionary by the American Board and at the close of 1822 sailed for Malta and thence the next year went to Beirut, where he aided in establishing the station which became the center of the Syrian mission.  In 1828, on account of threatened war between England and Turkey, the missionaries removed to Malta, where Goodell labored in preparing and printing books for the mission; until, in 1831, the way having been opened by the destruction of the Turkish fleet at Navarino, he went to Constantinople, where he commenced the Armeno-Turkish mission.  During his missionary life he and his devoted wife cheerfully endured many trials and perils and were compelled to move their residence 33 times in 29 years.  One of his chief labors was the translation of the Bible into Armeno-Turkish (Turkish written in Armenian letters), in making and revising which he spent 20 years.  In 1865, after 43 years of toil, he returned to the United States and died in Philadelphia at the residence of his son, Dr. William Goodell, on February 18, 1867.  Consult his life by Prime (New York, 1876).

Georgios Efrem: Georgios Efrem (Greek: Γεώργιος Εφραίμ ; born 5 July 1989) is a Cypriot international footballer who plays as a winger for APOEL in the Cypriot First Division.  He is a product of Arsenal F.C. Academy.

Walley Barnes: Walley Barnes (16 January 1920 – 4 September 1975) was a Welsh footballer and broadcaster.  He, playing as a Defender, featured for Southampton and Arsenal F.C. as well as captained the Welsh national side.

David O'Leary: David Anthony O'Leary (born 2 May 1958) is an Irish football manager and former player.  His managerial career began at Leeds United and later he managed Aston Villa.  He most recently worked as the manager of Al-Ahli Dubai.  The majority of his 20-year playing career was spent as a central defender at Arsenal.  O'Leary's tally of 722 appearances for the North London side stands as a club record.

Kamiar Ghanbari: Kamiar Ghanbari (Persian: کامیار قنبری‎ ‎ ; born 1988 in Tehran) is an Iranian football defender who currently plays for Persepolis F.C. in Iran's Premier Football League.  He is a talented left footed defender who can play in the left back and central defender position.  He has represented Iran in most youth levels.  He left the PAS Tehran F.C. youth system at the beginning of 2007 at the age of 19 after being approved by Hamid Estili he put pen to paper to a contract keeping him at Persepolis until 2010.

John Jensen: John Jensen (born 3 May 1965), nicknamed Faxe, is the head coach of the Danish club Fremad Amager in the second tier of the Danish league.  His playing career lasted over a decade, including a stint for Arsenal F.C. in England and three stints for Brøndby IF in Denmark.  He scored four goals in 69 caps for the Danish national team, entering Danish footballing folklore during the 1992 European Championship tournament, when he scored the opening goal in Denmark's 2–0 victory over Germany in the final.

Arsenal F.C. Academy: Arsenal Football Club Academy is the youth team setup of Arsenal Football Club based in Hale End, London, England.  The academy plays within the Professional Development League, the highest level of youth football in England.  The club as well features within the FA Youth Cup and the UEFA Youth League tourneys.  Ascending from the academy has been players such as David Rocastle, Liam Brady, John Radford, Terry Neill and Pat Rice.  As well footballers in the like of David O'Leary, Hector Bellerin and Charlie George have also emanated from Hale End.  The Netherland's Andries Jonker was in prior the head of the academy with Englishman Luke Hobbs now at the helm.

Kareem Omolaja: Kareem was born in a sports loving family.  His elder brother was also a footballer and Kareem started playing football getting inspired from his brother.  Though, Kareem is an ardent follower of Arsenal F.C. but he is a big admirer of former Real Madrid C.F. defender Fernando Hierro.  Kareem has a plan to open a football academy in future for the underprivileged children who are interested in football.

Hawi (film): Youssef, Ibrahim and Fady spent 20 years in the same prison.  Youssef has just been released in order to find several confidential documents.  After 20 years, Ibrahim wants to see his daughter again.  She is rehearsing with the third man, Fady, the musician.  Apart from these three men, in The Juggler, we will also meet an old horseman who hopes to heal his beloved animal and a TV presenter who needs a guest for his show.  They are all looking for someone or something in this kaleidoscopic portrait of loneliness and despair in today's Egypt.

Supporting paragraphs: Arsenal F.C. Academy David O'Leary
Answer: David O'Leary