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.

Example Input: Passage: Uranium carbides and uranium nitrides are both relatively inert semimetallic compounds that are minimally soluble in acids, react with water, and can ignite in air to form U
3O
8. Carbides of uranium include uranium monocarbide (UC), uranium dicarbide (UC
2), and diuranium tricarbide (U
2C
3). Both UC and UC
2 are formed by adding carbon to molten uranium or by exposing the metal to carbon monoxide at high temperatures. Stable below 1800 °C, U
2C
3 is prepared by subjecting a heated mixture of UC and UC
2 to mechanical stress. Uranium nitrides obtained by direct exposure of the metal to nitrogen include uranium mononitride (UN), uranium dinitride (UN
2), and diuranium trinitride (U
2N
3).
Example Output: Along with uranium monocarbide and uranium dicarbide, what is a unnotable carbide of uranium?

Example Input: Passage: The RIBA Guide to its Archive and History (1986) has a section on the "Statutory registration of architects" with a bibliography extending from a draft bill of 1887 to one of 1969. The Guide's section on "Education" records the setting up in 1904 of the RIBA Board of Architectural Education, and the system by which any school which applied for recognition, whose syllabus was approved by the Board and whose examinations were conducted by an approved external examiner, and whose standard of attainment was guaranteed by periodical inspections by a "Visiting Board" from the BAE, could be placed on the list of "recognized schools" and its successful students could qualify for exemption from RIBA examinations.
Example Output: When does the Royal Institute's Guide indicate the last RIBA Board was established?

Example Input: Passage: In 1902, the Siemens company developed a tantalum lamp filament. These lamps were more efficient than even graphitized carbon filaments and could operate at higher temperatures. Since tantalum metal has a lower resistivity than carbon, the tantalum lamp filament was quite long and required multiple internal supports. The metal filament had the property of gradually shortening in use; the filaments were installed with large loops that tightened in use. This made lamps in use for several hundred hours quite fragile. Metal filaments had the property of breaking and re-welding, though this would usually decrease resistance and shorten the life of the filament. General Electric bought the rights to use tantalum filaments and produced them in the US until 1913.
Example Output:
Who developed the tantalum light filament in 1905?