the intensity of light emitted by them changes with time
B.
the distance of the stars from the earth changes with time
C.
the refractive index of the different layers of the earth's atmosphere changes continuously, consequently the position of the image of a start changes with time
D.
the light from the star is scattered by the dust particles and air molecules in the earth's atmosphere
It takes much longer to cook food in the hills than in the plains, because
A.
in the hills the atmospheric pressure is lower than that in the plains and therefore water boils at a temperature lower than 100oC causing an increase in cooking time
B.
due to low atmospheric pressure on the hills, the water boils at a temperature higher than 100oC and therefore water takes longer to boi
C.
in the hills the atmospheric density is low and therefore a lot of heat is lost to the atmosphere
D.
in the hills the humidity is high and therefore a lot of heat is absorbed by the atmosphere leaving very little heat for cooking
