21. When air is blown into a balloon, it expands equally in all directions. The best explanation for this is (circle the correct answer): A - The gas molecules in the balloon are expanding B - Internal air pressure acts at right angles to the balloon surface. C - As more air is blown in, the temperature increases causing the balloon to expand.

C

Explanation:

I would have said B but air pressure acts at ALL angles(directions). C makes sense because the increase in the temperature would cause the molecules to bounce off the walls of the balloon and each other which exerts pressure.

as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

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