Teacher: In this task, you're given a question, along with three passages, 1, 2, and 3. Your job is to determine which passage can be used to answer the question by searching for further information using terms from the passage. Indicate your choice as 1, 2, or 3.
Teacher: Now, understand the problem? If you are still confused, see the following example:
Question: When did the operation during which the 704th dropped supplies to allied troops near Nijmegen begin? Passage 1: The group was occasionally diverted from strategic missions to carry out air support and interdiction missions. It supported Operation Overlord, the invasion of Normandy by attacking transportation targets, including bridges, along with airfields and strong points in France. On D Day, the squadron and the rest of the 446th Group led the first heavy bomber mission of the day. The 446th aided ground forces at Caen and Saint-Lô during July by hitting bridges, gun batteries, and enemy troops. During Operation Market Garden, the attempt to seize a bridgehead across the Rhine in the Netherlands, the 704th dropped supplies to allied troops near Nijmegen. It struck lines of communications during the Battle of the Bulge. During Operation Varsity in March 1945, it supplied ground and airborne troops near Wesel. The squadron flew its last combat mission on 25 April 1945 against Salzburg, Austria. The group had flown 273 missions and had lost 58 aircraft during the war,
. Passage 2: John Ford (1894–1973) was an American film director whose career spanned from 1913 to 1971. During this time he directed more than 140 films. Born in Maine, Ford entered the filmmaking industry shortly after graduating from high school with the help of his older brother, Francis Ford, who had established himself as a leading man and director for Universal Studios. After working as an actor, assistant director, stuntman, and prop man – often for his brother – Universal gave Ford the opportunity to direct in 1917. Initially working in short films, he quickly moved into features, largely with Harry Carey as his star. In 1920 Ford left Universal and began working for the Fox Film Corporation. During the next ten years he directed more than 30 films, including the westerns The Iron Horse (1924) and 3 Bad Men (1926), both starring George O'Brien, the war drama Four Sons and the Irish romantic drama Hangman's House (both 1928 and both starring Victor McLaglen). In the same year of these last two films, Ford directed his first all-talking film, the short Napoleon's Barber. The following year he directed his first all-talking feature, The Black Watch.
. Passage 3: Since the late 1970s, the central part of NYU is its Washington Square campus in the heart of Greenwich Village. Despite being public property, and expanding the Fifth Avenue axis into Washington Square Park, the Washington Square Arch is the unofficial symbol of NYU. Until 2008, NYU's commencement ceremony was held in Washington Square Park. However, due to space constraints, ceremonies are now held at the Yankee Stadium. Important facilities at Washington Square are the Elmer Holmes Bobst Library, designed by Philip Johnson and Richard Foster, who also designed several other structures, such as Tisch Hall, Meyer Hall, and the Hagop Kevorkian Center. When designing these buildings Johnson and Foster also set up a master plan for a complete redesign of the NYU Washington Square campus. However, it was never implemented. Other historic buildings include the Silver Center (formerly known as "Main building"); the Brown Building of Science; Judson Hall, which houses the King Juan Carlos I of Spain Center; Vanderbilt Hall, the historic townhouse row on Washington Square North; The Grey Art Gallery at 100 Washington Square East, housing the New York University art collection and featuring museum quality exhibitions; the Kaufman Management Center; and the Torch Club – the NYU dining and club facility for alumni, faculty, and administrators. Just a block south of Washington Square is NYU's Washington Square Village, housing graduate students and junior and senior faculty residences in the Silver Towers, designed by I. M. Pei, where an enlargement of Picasso's sculpture Bust of Sylvette (1934) is displayed.
.
Solution: 1
Reason: The question refers to the 704th unit and task about war which is decribed by Passage 1.

Now, solve this instance: Question: What is the other extracellular loop linked by? Passage 1:A return to the Formula Three Euroseries beckoned for van Dam, with a 2009 campaign for Kolles & Heinz Union, the new team set up by Colin Kolles and Werner Heinz. However, the partnership was not to last, as after the rounds at Lausitz, van Dam parted company with the team. In four races, his best finish was eighteenth during the season-opening race at Hockenheim. Van Dam drove in the 24-hour endurance races at the Nürburgring and at Spa, before agreeing to drive the car of PSV Eindhoven in the Superleague Formula series. He replaced Dominick Muermans in the car, with the team lying eighteenth in the overall standings. However, he returned to the Euroseries, for the Barcelona rounds, rejoining his former team SG Formula.
 Passage 2:Chemokine receptors are G protein-coupled receptors containing 7 transmembrane domains that are found predominantly on the surface of leukocytes, making it one of the rhodopsin-like receptors. Approximately 19 different chemokine receptors have been characterized to date, which share many common structural features; they are composed of about 350 amino acids that are divided into a short and acidic N-terminal end, seven helical transmembrane domains with three intracellular and three extracellular hydrophilic loops, and an intracellular C-terminus containing serine and threonine residues that act as phosphorylation sites during receptor regulation. The first two extracellular loops of chemokine receptors are linked together by disulfide bonding between two conserved cysteine residues. The N-terminal end of a chemokine receptor binds to chemokine(s) and is important for ligand specificity. G-proteins couple to the C-terminal end, which is important for receptor signaling following ligand binding. Although chemokine receptors share high amino acid identity in their primary sequences, they typically bind a limited number of ligands. Chemokine receptors are redundant in their function as more than one chemokine is able to bind to a single receptor.
 Passage 3:Golubić completed his primary education in Stolac, before relocating to Sarajevo to attend high school. In 1908, he moved to Belgrade for post-secondary studies, studying law at the University of Belgrade. Some of Golubić's classmates and contemporaries later recounted that Golubić was recruited by the Russian secret police, the Okhrana, in his youth. The historian Vladimir Dedijer later consulted the records of the Hoover Institution in an attempt to verify this claim, to no avail. Golubić did join Young Bosnia (), a multi-ethnic youth organization agitating for the separation of Bosnia and Herzegovina from Austria-Hungary. The organization's membership was around 70 percent Serb, 20 percent Bosnian Muslim and 10 percent Croat. Following the outbreak of the Balkan Wars in November 1912, Golubić joined the volunteer Chetnik detachment of Major Vojislav Tankosić. As part of their training, Tankosić ordered that Golubić and the other volunteers jump into the Sava from a railway bridge, "just to see whether you are going to fulfill all my orders."

Student:
2