Answer:
If Exosphere is not an option, then it would be Thermosphere
I fill like the reaction would be distillation or chromatography but distillation has to do with bioling points and chromatography has to do with how far the components separate along the material. but im in chemistry not advance placement.
For this case we have that by definition, a linear function is of the form 
If we have that a and b are linear functions, then they are of the form:

If we multiply them we have: (Applying distributive property)

That is, we get a quadratic function.
Answer:
