Problem: Extract the answer to the question from the following context. Question: How do we know the American civilizations were scientifically very advanced? Context: According to both indigenous American and European accounts and documents, American civilizations at the time of European encounter had achieved many accomplishments. For instance, the Aztecs built one of the largest cities in the world, Tenochtitlan, the ancient site of Mexico City, with an estimated population of 200,000. American civilizations also displayed impressive accomplishments in astronomy and mathematics. The domestication of maize or corn required thousands of years of selective breeding.

A: The domestication of maize or corn required thousands of years of selective breeding

Problem: Extract the answer to the question from the following context. Question: What was Willibrordus' title in one word? Context: By the mid-7th century, English and Irish missionaries set out to convert the Frisians. The pope appointed their leader, Willibrordus, bishop of the Frisians. The tenure of Willibrordus is generally considered to be the beginning of the Bishopric of Utrecht. In 723, the Frankish leader Charles Martel bestowed the fortress in Utrecht and the surrounding lands as the base of the bishops. From then on Utrecht became one of the most influential seats of power for the Roman Catholic Church in the Netherlands. The archbishops of Utrecht were based at the uneasy northern border of the Carolingian Empire. In addition, the city of Utrecht had competition from the nearby trading centre Dorestad. After the fall of Dorestad around 850, Utrecht became one of the most important cities in the Netherlands. The importance of Utrecht as a centre of Christianity is illustrated by the election of the Utrecht-born Adriaan Florenszoon Boeyens as pope in 1522 (the last non-Italian pope before John Paul II).

A: bishop

Problem: Extract the answer to the question from the following context. Question: Which president was not assassinated? Context: In 1864, Andrew Johnson (a War Democrat from Tennessee) was elected Vice President under Abraham Lincoln. He became President after Lincoln's assassination in 1865. Under Johnson's lenient re-admission policy, Tennessee was the first of the seceding states to have its elected members readmitted to the U.S. Congress, on July 24, 1866. Because Tennessee had ratified the Fourteenth Amendment, it was the only one of the formerly secessionist states that did not have a military governor during the Reconstruction period.

A: Andrew Johnson

Problem: Extract the answer to the question from the following context. Question: The capital of the country of Serbia is? Context: On 6 April 1941, German forces, with Hungarian and Italian assistance, launched an invasion of Yugoslavia. On 10 April 1941, Slavko Kvaternik proclaimed the Independent State of Croatia, and Tito responded by forming a Military Committee within the Central Committee of the Yugoslav Communist Party. Attacked from all sides, the armed forces of the Kingdom of Yugoslavia quickly crumbled. On 17 April 1941, after King Peter II and other members of the government fled the country, the remaining representatives of the government and military met with the German officials in Belgrade. They quickly agreed to end military resistance. On 1 May 1941, Tito issued a pamphlet calling on the people to unite in a battle against the occupation. On 27 June 1941, the Central Committee of the Communist Party of Yugoslavia appointed Tito Commander in Chief of all project national liberation military forces. On 1 July 1941, the Comintern sent precise instructions calling for immediate action.

A:
Belgrade