Background: David Thompson was born in Westminster, Middlesex, to recent Welsh migrants David and Ann Thompson. When Thompson was two, his father died. Due to the financial hardship with his mother without resources, Thompson and his older brother were placed in the Grey Coat Hospital, a school for the disadvantaged of Westminster. Thompson graduated to the Grey Coat mathematical school, where he was introduced to basic navigation skills.
Context: Thompson's decision to defect to the North West Company in 1797 without providing the customary one-year notice was not well received by his former employers. But the North West Company was more supportive of Thompson pursuing his interest in surveying and work on mapping the interior of what was to become Canada, as they judged it in the company's long-term interest. In 1797, Thompson was sent south by his employers to survey part of the Canada-US boundary along the water routes from Lake Superior to Lake of the Woods to satisfy unresolved questions of territory arising from the Jay Treaty between Great Britain and the United States after the American Revolutionary War. By 1798 Thompson had completed a survey of 6,750 km (4,190 mi) from Grand Portage, through Lake Winnipeg, to the headwaters of the Assiniboine and Mississippi rivers, as well as two sides of Lake Superior. In 1798, the company sent him to Red Deer Lake (Lac La Biche in present-day Alberta) to establish a trading post. (The English translation of Lac la Biche: Red Deer Lake, was first recorded on the Mackenzie map of 1793.) Thompson spent the next few seasons trading based in Fort George (now in Alberta), and during this time led several expeditions into the Rocky Mountains. In 1804, at the annual meeting of the North West Company in Kaministiquia, Thompson was made a full partner of the company. He spent the next few seasons based there managing the fur trading operations but still finding time to expand his surveys of the waterways around Lake Superior. At the 1806 company meeting, officers decided to send Thompson back out into the interior. Concern over the American-backed expedition of Lewis and Clark prompted the North West Company to charge Thompson with the task of finding a route to the Pacific to open up the lucrative trading territories of the Pacific Northwest.
Question: Did he do a third significant survey ?
Answer: finding a route to the Pacific to open up the lucrative trading territories of the Pacific Northwest.

Problem: Background: Daniel Barenboim (born 15 November 1942) is an Argentine-Israeli pianist and conductor who is a citizen of Argentina, Israel, Palestine, and Spain. He is the general music director of the Berlin State Opera, and the Staatskapelle Berlin; he previously served as Music Director of the Chicago Symphony Orchestra, the Orchestre de Paris and La Scala in Milan. Barenboim is known for his work with the West-Eastern Divan Orchestra, a Seville-based orchestra of young Arab and Israeli musicians, and as a resolute critic of the Israeli occupation of Palestinian territories. Barenboim has received many awards and prizes, including an honorary Knight Commander of the Order of the British Empire, France's Legion d'honneur both as a Commander and Grand Officier, and the German Grosses Bundesverdienstkreuz and Willy Brandt Award.
Context: Daniel Barenboim was born in 1942 in Buenos Aires, Argentina, to Argentinian-Jewish parents Aida (nee Schuster) and Enrique Barenboim. He started piano lessons at the age of five with his mother, continuing to study with his father, who remained his only teacher. On 19 August 1950, at the age of seven, he gave his first formal concert in his hometown, Buenos Aires. In 1952, Barenboim's family moved to Israel. Two years later, in the summer of 1954, his parents took him to Salzburg to take part in Igor Markevitch's conducting classes. During that summer he also met and played for Wilhelm Furtwangler, who has remained a central musical influence and ideal for Barenboim. Furtwangler called the young Barenboim a "phenomenon" and invited him to perform the Beethoven First Piano Concerto with the Berlin Philharmonic, but Barenboim's father considered it too soon after the Second World War for a child of Jewish parents to be performing in Berlin. In 1955 Barenboim studied harmony and composition with Nadia Boulanger in Paris. On 15 June 1967, Barenboim and British cellist Jacqueline du Pre were married in Jerusalem at a Western Wall ceremony, Du Pre having converted to Judaism. Acting as one of the witnesses was the conductor Zubin Mehta, a long-time friend of Barenboim. Since "I was not Jewish I had to temporarily be renamed Moshe Cohen, which made me a 'kosher witness'," Mehta recalled. Du Pre retired from music in 1973, after being diagnosed with multiple sclerosis (MS). The marriage lasted until du Pre's death in 1987. In the early 1980s, Barenboim began an affair with the Russian pianist Elena Bashkirova, with whom he had two sons born in Paris before du Pre's death: David Arthur, born 1983, and Michael, born 1985. Barenboim worked to keep his relationship with Bashkirova hidden from du Pre, and believed he had succeeded. He and Bashkirova married in 1988. Both sons are part of the music world: David is a manager-writer for the German hip-hop band Level 8, and Michael Barenboim is a classical violinist.
Question: Who was a witness to their marriage?
Answer:
Acting as one of the witnesses was the conductor Zubin Mehta, a long-time