Use a disfluent question or a proper question and find the answer to the question based on the given context or return None if an answer can't be found. A disfluent question is a question that has some interruptions in it while framing. A proper question is the correct form of the question without any disfluency.

Example input: proper question: In what year did the U of C become one of 7 founding members of the Association of Chicago Universities? 
 disfluent question: In what year did Robert Harper or did the U of C become one of 7 founding members of the Association of Chicago Universities? 
 context: Founded by the American Baptist Education Society with a donation from oil magnate and wealthiest man in history John D. Rockefeller, the University of Chicago was incorporated in 1890; William Rainey Harper became the university's first president in 1891, and the first classes were held in 1892. Both Harper and future president Robert Maynard Hutchins advocated for Chicago's curriculum to be based upon theoretical and perennial issues rather than on applied sciences and commercial utility. With Harper's vision in mind, the University of Chicago also became one of the 14 founding members of the Association of American Universities, an international organization of leading research universities, in 1900.
Example output: None
Example explanation: The answer to the above question is not found from the context hence it is not answerable so the output is 'None' so it is a positive example.
Q: proper question: What has a classification system for construction companies? 
 disfluent question: What has a category no make that a classification system for construction companies? 
 context: The Standard Industrial Classification and the newer North American Industry Classification System have a classification system for companies that perform or otherwise engage in construction. To recognize the differences of companies in this sector, it is divided into three subsectors: building construction, heavy and civil engineering construction, and specialty trade contractors. There are also categories for construction service firms (e.g., engineering, architecture) and construction managers (firms engaged in managing construction projects without assuming direct financial responsibility for completion of the construction project).
A:
Standard Industrial Classification