This task is about creating an unanswerable question based on a given passage. Construct a question that looks relevant to the given context but is unanswerable. Following are a few suggestions about how to create unanswerable questions:
(i) create questions which require satisfying a constraint that is not mentioned in the passage
(ii) create questions which require information beyond what is provided in the passage in order to answer
(iii) replace an existing entity, number, date mentioned in the passage with other entity, number, date and use it in the question
(iv) create a question which is answerable from the passage and then replace one or two words by their antonyms or insert/remove negation words to make it unanswerable.
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Question: Passage: On 24 August, Pravda and Izvestia carried news of the non-secret portions of the Pact, complete with the now infamous front-page picture of Molotov signing the treaty, with a smiling Stalin looking on. The news was met with utter shock and surprise by government leaders and media worldwide, most of whom were aware only of the British–French–Soviet negotiations that had taken place for months. The Molotov–Ribbentrop Pact was received with shock by Nazi Germany's allies, notably Japan, by the Comintern and foreign communist parties, and by Jewish communities all around the world. So, that day, German diplomat Hans von Herwarth, whose grandmother was Jewish, informed Guido Relli, an Italian diplomat, and American chargé d'affaires Charles Bohlen on the secret protocol regarding vital interests in the countries' allotted "spheres of influence", without revealing the annexation rights for "territorial and political rearrangement".

Answer: Which diplomat never leaked information about the secret agreements?


Question: Passage: Dallin H. Oaks replaced Wilkinson as president in 1971. Oaks continued the expansion of his predecessor, adding a law school and proposing plans for a new School of Management. During his administration, a new library was also added, doubling the library space on campus. Jeffrey R. Holland followed as president in 1980, encouraging a combination of educational excellence and religious faith at the university. He believed that one of the school's greatest strengths was its religious nature and that this should be taken advantage of rather than hidden. During his administration, the university added a campus in Jerusalem, now called the BYU Jerusalem Center. In 1989, Holland was replaced by Rex E. Lee. Lee was responsible for the Benson Science Building and the Museum of Art on campus. A cancer victim, Lee is memorialized annually at BYU during a cancer fundraiser called the Rex Lee Run. Shortly before his death, Lee was replaced in 1995 by Merrill J. Bateman.

Answer: Who replaced Wilkinson as president in 1980?


Question: Passage: Beginning in the 1940s and continuing into the 1970s, the bureau investigated cases of espionage against the United States and its allies. Eight Nazi agents who had planned sabotage operations against American targets were arrested, and six were executed (Ex parte Quirin) under their sentences. Also during this time, a joint US/UK code-breaking effort (the Venona project)—with which the FBI was heavily involved—broke Soviet diplomatic and intelligence communications codes, allowing the US and British governments to read Soviet communications. This effort confirmed the existence of Americans working in the United States for Soviet intelligence. Hoover was administering this project but failed to notify the Central Intelligence Agency (CIA) until 1952. Another notable case is the arrest of Soviet spy Rudolf Abel in 1957. The discovery of Soviet spies operating in the US allowed Hoover to pursue his longstanding obsession with the threat he perceived from the American Left, ranging from Communist Party of the United States of America (CPUSA) union organizers to American liberals.

Answer:
What did the bureau investigate before the 1940s?