Which combination of a wire coil and a core would make the weakest electromagnet?
O A. 20 coils of bare wire around a steel core
B. 20 coils of insulated wire around a hollow cardboard core
O C. 50 coils of insulated wire around a hollow cardboard core
D. 50 coils of bare wire around a steel bolt

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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answer///terminator or twilight zone;