It's C, angle of incidence is equal to angle of reflection
Different densities have to have a reason - different pressure and/or humidity etc. If there is a different pressure, there is a mechanical force that preserves the pressure difference: think about the cyclones that have a lower pressure in the center. The cyclones rotate in the right direction and the cyclone may be preserved by the Coriolis force.
If the two air masses differ by humidity, the mixing will almost always lead to precipitation - which includes a phase transition for water etc. It's because the vapor from the more humid air mass gets condensed under the conditions of the other. You get some rain. In general, intense precipitation, thunderstorms, and other visible isolated weather events are linked to weather fronts.
At any rate, a mixing of two air masses is a nontrivial, violent process in general. That's why the boundary is called a "front". In the military jargon, a front is the contested frontier of a conflict. So your idea that the air masses could mix quickly and peacefully - whatever you exactly mean quantitatively - either neglects the inertia of the air, a relatively low diffusion coefficient, a low thermal conductivity, and/or high latent heat of water vapor. A front is something that didn't disappear within minutes so pretty much tautologically, there must be forces that make such a quick disappearance impossible.
<span>Compunction is similar to an obligation; if you are "under compunction," then you are bound by some debt or sentence to do something. Repentance is actually an action rather than a feeling or condition: it is an act of the will which disowns whatever behavior you regret, and to repent implies a determination not to make the same mistake again. Contrition is the expressed emotion of being sorry for something; if you went to a person you had wronged, to make amends and ask their forgiveness, you would be "contrite" toward them. Remorse is simply another word for regret - you feel bad within yourself, either for what you did or for how the consequences affected you.</span>
34.916 is the answer to 67.786-32.87 . I found this answer by using a calculator.
