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: The noise-based speed is defined as the exposure that will lead to a given signal-to-noise ratio on individual pixels. Two ratios are used, the 40:1 ("excellent image quality") and the 10:1 ("acceptable image quality") ratio. These ratios have been subjectively determined based on a resolution of 70 pixels per cm (178 DPI) when viewed at 25 cm (9.8 inch) distance. The signal-to-noise ratio is defined as the standard deviation of a weighted average of the luminance and color of individual pixels. The noise-based speed is mostly determined by the properties of the sensor and somewhat affected by the noise in the electronic gain and AD converter.

Answer: Which ratio was subjectively determined?


Question: Passage: The South Saharan steppe and woodlands ecoregion is a narrow band running east and west between the hyper-arid Sahara and the Sahel savannas to the south. Movements of the equatorial Intertropical Convergence Zone (ITCZ) bring summer rains during July and August which average 100 to 200 mm (3.9 to 7.9 in) but vary greatly from year to year. These rains sustain summer pastures of grasses and herbs, with dry woodlands and shrublands along seasonal watercourses. This ecoregion covers 1,101,700 km2 (425,400 mi2) in Algeria, Chad, Mali, Mauritania, and Sudan.

Answer: what ecoregion runs north and south in a norrow band?


Question: Passage: Numerous regional transportation projects have occurred in recent years to mitigate congestion in San Diego. Notable efforts are improvements to San Diego freeways, expansion of San Diego Airport, and doubling the capacity of the cruise ship terminal of the port. Freeway projects included expansion of Interstates 5 and 805 around "The Merge," a rush-hour spot where the two freeways meet. Also, an expansion of Interstate 15 through the North County is underway with the addition of high-occupancy-vehicle (HOV) "managed lanes". There is a tollway (The South Bay Expressway) connecting SR 54 and Otay Mesa, near the Mexican border. According to a 2007 assessment, 37 percent of streets in San Diego were in acceptable driving condition. The proposed budget fell $84.6 million short of bringing the city's streets to an acceptable level. Port expansions included a second cruise terminal on Broadway Pier which opened in 2010. Airport projects include expansion of Terminal 2, currently under construction and slated for completion in summer 2013.

Answer:
What is the name given to the highly congested spot where Interstates 85 and 805 meet?