Teacher: In this task, you're given a question, a context passage, and four options which are terms from the passage. After reading a passage, you will get a brief understanding of the terms. Your job is to determine by searching and reading further information of which term you can answer the question. Indicate your choice as 'a', 'b', 'c', or 'd'. If you think more than one option is plausible, choose the more probable option to help you answer the question.
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: 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-Lôduring 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,
. Links: a. Allies of World War II b. Wesel c. Operation Market Garden d. Air Support.
Solution: c
Reason: The passage describes the 704th's actions during Operation Market Garden.

Now, solve this instance: Question: What country was the location of the castle that was exchanged for Dinaburg Castle? Passage:Traidenis, known for his devotion to paganism and anti-German attitude, was also successful in fighting with the Livonian Order. In 1270 he won the Battle of Karuse, fought on ice near Saaremaa, and killed Otto von Lutterberg, master of the Order. A new master, Andreas von Westfalen, sought a quick revenge, but was also killed by Traidenis. However, by 1272 the Order retaliated, attacking Semigalia and building Dinaburg Castle in 1273 on lands nominally controlled by Traidenis. Despite four siege engines used to throw stones, he was unable to capture the new fortress and had to retreat in 1278. In 1279 the order attacked Lithuanian lands, reaching as far as Kernavė, but on their way back they suffered a great defeat in the Battle of Aizkraukle. The Order's master, Ernst von Rassburg, became the third master to be killed by Traidenis. The defeat encouraged conquered Semigallians to rebel. The Semigalians, led by Nameisis, were now willing to acknowledge Lithuania's superiority and asked Traidenis for assistance. In 1281, Traidenis conquered Jersika Castle in the present-day Preiļi District, and was able to exchange it for Dinaburg Castle. However, Traidenis died soon afterwards, and assistance to Semigalians, exhausted by constant warfare, diminished. Traidenis is the first known Lithuanian duke to have died a natural death. All others before him were assassinated or killed in battle.
 Links: a. Principality of Jersika b. Dinaburga Castle c. Otto von Lutterberg d. Livonian Order
Student:
a