In this task, you're expected to write answers to questions involving multiple references to the same entity. The answer to the question should be unambiguous and a phrase in the paragraph. Most questions can have only one correct answer.

[EX Q]: Passage: Three years after the destruction of the Death Star, the Rebel Alliance, led by Princess Leia, has set up a new base on the ice planet of Hoth. The Imperial fleet, led by Darth Vader, continues to hunt for the new Rebel base by dispatching probe droids across the galaxy. Luke Skywalker is captured by a wampa while investigating one such probe, but manages to escape from the wampa's lair with his lightsaber. Before Luke succumbs to hypothermic sleep, the Force ghost of his late mentor, Obi-Wan Kenobi, instructs him to go to Dagobah to train under Jedi Master Yoda. Han Solo locates Luke and cuts open the tauntaun he rode there on to keep his friend warm; they wait there until being rescued by a search party the next morning.
Meanwhile, the probe alerts the Imperial fleet to the Rebels' location. The Empire launches a large-scale attack using AT-AT walkers to capture the base, which forces the Rebels to retreat. Han and Leia escape with C-3PO and Chewbacca on the Millennium Falcon, but the ship's hyperdrive malfunctions. They hide in an asteroid field, where Han and Leia grow closer amidst tension and briefly kiss. Vader summons bounty hunters to assist in finding the Falcon. Luke, meanwhile, escapes with R2-D2 in his X-wing fighter and crash-lands on the swamp planet of Dagobah. He meets a diminutive creature who reveals himself to be Yoda; after conferring with Obi-Wan's spirit, Yoda reluctantly accepts Luke as his student. 
Question: Who is told to go train under Yoda?
[EX A]: Luke.

[EX Q]: Passage: There is considerable uncertainty about the identities of the Grand Dukes of Lithuania between Traidenis' death in 1282 and Vytenis' assumption of power in 1295. This is in part because the two main sources for Lithuanian history in the 13th century, the Hypatian Codex and the Livonian Rhymed Chronicle, end in the early 1290s. In 1285, one chronicle mentions Daumantas as Grand Duke. He attacked the Bishop of Tver and was severely wounded or even killed in the battle. However, that is the only information about him.
The Gediminid dynasty began its ascent in Lithuania during this time with the emergence of its first leader, Butigeidis. In 1289, leading about 8,000 troops, he attacked Sambia. In 1289 the Teutonic Knights built a castle in present-day Sovetsk (Tilsit) and their raids intensified. Butigeidis was the first to build strong castles along the Neman River. He died in 1290 or 1292, and his brother Butvydas (also known as Pukuveras) inherited the crown. Butvydas was the father of Vytenis and probably of Gediminas. During his short reign Butvydas tried to defend the duchy against the Teutonic Knights; he also attacked Masovia, an ally of the knights. His son, Vytenis, advanced to power in 1295 and ended the period of relative instability. His reign marks the transition from the state's establishment to the point at which it was poised for expansion. 
Question: What is the alias of the person that inherited the crown from Butigeidis?
[EX A]: Pukuveras.

[EX Q]: Passage: Kozelsk and Starobelsk were used mainly for military officers, while Ostashkov was used mainly for Polish Scouting, gendarmes, police officers, and prison officers. Some prisoners were members of other groups of Polish intelligentsia, such as priests, landowners, and law personnel. The approximate distribution of men throughout the camps was as follows: Kozelsk, 5000; Ostashkov, 6570; and Starobelsk, 4000. They totalled 15,570 men.According to a report from 19 November 1939, the NKVD had about 40,000 Polish POWs: 8,000-8,500 officers and warrant officers, 6,000-6,500 officers of police, and 25,000 soldiers and non-commissioned officers who were still being held as POWs. In December, a wave of arrests resulted in the imprisonment of additional Polish officers. Ivan Serov reported to Lavrentiy Beria on 3 December that "in all, 1,057 former officers of the Polish Army had been arrested". The 25,000 soldiers and non-commissioned officers were assigned to forced labor (road construction, heavy metallurgy).Once at the camps, from October 1939 to February 1940, the Poles were subjected to lengthy interrogations and constant political agitation by NKVD officers, such as Vasily Zarubin. The prisoners assumed they would be released soon, but the interviews were in effect a selection process to determine who would live and who would die. According to NKVD reports, if a prisoner could not be induced to adopt a pro-Soviet attitude, he was declared a "hardened and uncompromising enemy of Soviet authority".On 5 March 1940, pursuant to a note to Joseph Stalin from Beria, six members of the Soviet Politburo — Stalin, Vyacheslav Molotov, Lazar Kaganovich, Kliment Voroshilov, Anastas Mikoyan, and Mikhail Kalinin — signed an order to execute 25,700 Polish "nationalists and counterrevolutionaries" kept at camps and prisons in occupied western Ukraine and Belarus. The reason for the massacre, according to the historian Gerhard Weinberg, was that Stalin wanted to deprive a potential future Polish military of a large portion of its talent:
It has been suggested that the motive for this terrible step [the Katyn massacre] was to reassure the Germans as to the reality of Soviet anti-Polish policy. This explanation is completely unconvincing in view of the care with which the Soviet regime kept the massacre secret from the very German government it was supposed to impress. […] A more likely explanation is that [the massacre] should be seen as looking forward to a future in which there might again be a Poland on the Soviet Union's western border. Since he intended to keep the eastern portion of the country in any case, Stalin could be certain that any revived Poland would be unfriendly. Under those circumstances, depriving it of a large proportion of its military and technical elite would make it weaker. 
Question: What is the name of the massacre about which Weinberg writes a more likely explanation is that it "should be seen as looking forward to a future in which there might again be a Poland on the Soviet Union's western border"?
[EX A]:
Katyn massacre.