You are given a passage. You need to construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) its answer is the whole paragraph. Avoid creating questions that can be answered correctly without actually understanding the paragraph.

Contrails are caused by water in the exhaust of jet engines and then freezing in the upper atmosphere.  It's basically the same thing as a cirrus cloud.  High performance airplanes can make white trails off their wingtips or on top of their wings which is caused by low pressure which in turn reduces the amount of water that is naturally in the air that the air can hold and it forms a cloud.  An interesting side note is that long contrails = high relative humidity, short contrails = low realitve humidity.
why sometimes a white foggy line or trail made behind the airplane in the sky.?

It's an acronym for a West African Pig.\n\nPreferred Scientific Name\n\nWest African pig \n\n\nAcronyms\n\nNIGERHYB (English)\n\nCommon Names\n\nEnglish \nImproved Nigerian Indigenous \nNigerian Native \nWest African Dwarf Pig \n\n\nCameroon \nBakosi \n\n\nGhana \nAshanti Dwarf \n\n\nNigeria \nElede \nOhan \n\n\nDAD-IS Main Common\nAshanti Dwarf \nBakosi \nNigerian Native \nWest African \n\nDAD-IS Local Names\nAshanti Black \nLocal Black \nNigerian Indigenous\n\n\n(**  )<|\nDead Fish\nOllec, the Fish Slayer
What is NIGERHYB?

There are such values, called R-values.  They define the resistance to heat loss per unit time, temperature difference and area (i.e., higher is better).  These are English units, hour-degreeF-ft^2/BTU.  An R-value of 20 means that 100 sq. ft. of wall separating a 20 deg F temperature difference for 8 hours passes 800 BTU of heat.  Typical recommended R-values (ref. 1) for use in residences are 4 to 60, depending on climate and location in the house.  For walls the range is 11 to 28.  In the ref. 2 web site you can find R ratings for various insulation materials, in R-value per inch of insulation thickness, and thicknesses required for various recommended R-values.

What's the rate of heat loss through a domestic well-insulated wall per sqm when the heat differential is 15C?

