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.

Q: Passage: Selenizza is a naturally occurring solid hydrocarbon bitumen found in the native asphalt deposit of Selenice, in Albania, the only European asphalt mine still in use. The rock asphalt is found in the form of veins, filling cracks in a more or less horizontal direction. The bitumen content varies from 83% to 92% (soluble in carbon disulphide), with a penetration value near to zero and a softening point (ring & ball) around 120 C. The insoluble matter, consisting mainly of silica ore, ranges from 8% to 17%.

A: The soluble matter consists mainly of silica ore and ranges from what percentage?
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Q: Passage: There has, however, been interest among railroad operators in returning to DC use at higher voltages than previously used. At the same voltage, DC often has less loss than AC, and for this reason high-voltage direct current is already used on some bulk power transmission lines. DC avoids the electromagnetic radiation inherent with AC, and on a railway this also reduces interference with signalling and communications and mitigates hypothetical EMF risks. DC also avoids the power factor problems of AC. Of particular interest to railroading is that DC can supply constant power with a single ungrounded wire. Constant power with AC requires three-phase transmission with at least two ungrounded wires. Another important consideration is that mains-frequency 3-phase AC must be carefully planned to avoid unbalanced phase loads. Parts of the system are supplied from different phases on the assumption that the total loads of the 3 phases will even out. At the phase break points between regions supplied from different phases, long insulated supply breaks are required to avoid them being shorted by rolling stock using more than one pantograph at a time. A few railroads have tried 3-phase but its substantial complexity has made single-phase standard practice despite the interruption in power flow that occurs twice every cycle. An experimental 6 kV DC railway was built in the Soviet Union.

A: Railroad operators have shown little interest in returning to what?
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Q: Passage: CBC Television stations can be received in many United States communities along the Canadian border over-the-air and have a significant audience in those areas. Such a phenomenon can also take place within Great Lakes communities such as Ashtabula, Ohio, which received programming from the CBC's London, Ontario, transmitter, based upon prevailing atmospheric conditions over Lake Erie. As of September 2010 CBC shut down its analogue transmitter and decided not to replace it with a digital transmitter. As a result, there is now a giant hole in the coverage of CBC in South-Western Ontario. Both CBC - Toronto and CBC - Windsor are both over 100 miles from London, ON and out of range for even the largest antennas[citation needed].

A:
What location in the United States has the highest viewership of CBC programming?
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