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: When Estonia was invaded and occupied by the Soviet Union in World War II, the status of the Estonian language changed to the first of two official languages (Russian being the other one). As with Latvia many immigrants entered Estonia under Soviet encouragement. In the second half of the 1970s, the pressure of bilingualism (for Estonians) intensified, resulting in widespread knowledge of Russian throughout the country. The Russian language was termed as 'the language of friendship of nations' and was taught to Estonian children, sometimes as early as in kindergarten. Although teaching Estonian to non-Estonians in schools was compulsory, in practice learning the language was often considered unnecessary.

Answer: What country did not occupy Estonia?

Question: Passage: Indonesia is the largest country in Southeast Asia and it also the largest archipelago in the world by size (according to the CIA World Factbook). Geologically, the Indonesian Archipelago is one of the most volcanically active regions in the world. Geological uplifts in the region have also produced some impressive mountains, culminating in Puncak Jaya in Papua, Indonesia at 5,030 metres (16,500 feet), on the island of New Guinea; it is the only place where ice glaciers can be found in Southeast Asia. The second tallest peak is Mount Kinabalu in Sabah, Malaysia on the island of Borneo with a height of 4,095 metres (13,435 feet). The highest mountain in Southeast Asia is Hkakabo Razi at 5,967 meters and can be found in northern Burma sharing the same range of its parent peak, Mount Everest.

Answer: What is the largest country in Asia?

Question: Passage: In 1579 the northern seven provinces signed the Union of Utrecht, in which they decided to join forces against Spanish rule. The Union of Utrecht is seen as the beginning of the Dutch Republic. In 1580 the new and predominantly Protestant state abolished the bishoprics, including the archbishopric of Utrecht. The stadtholders disapproved of the independent course of the Utrecht bourgeoisie and brought the city under much more direct control of the republic; which shifted the power towards its dominant province Holland. This was the start of a long period of stagnation of trade and development in Utrecht. Utrecht remained an atypical city in the new republic with about 40% Catholic in the mid-17th century, and even more among the elite groups, who included many rural nobility and gentry with town houses there.

Answer:
Who signed the Union of Utrecht in the 15th century?