The advantage of using a machine is that we apply less ??? at the input for the work done at the output. Please fill in the question mark area...Thank you much appreciated.

b.

explanation:

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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