The answer is "the ice-caps" from the north and south pole.
Answer:
The correct answer would be acrylic glass.
It can be explained with the help of refractive index.
It is a dimensionless number used to describe that how fast a light can propagate through a material.
Thus, the more the refractive index the more will be the bending.
Acrylic glass has the least refractive index as compared to the other materials provided.
Thus, the light would bend the least if acrylic glass would be used.
The two are potassium and rubidium. Why? Na is an alkali metal. As you go down the metals become more reactive.
Calcium has 20 protons. Why? The atomic # is 20 (the one at the top).
It has 20 neutrons. Why? The atomic mass (the number on the bottom) is ~40, ignoring electron mass. 40- 20 protons = 20 neutrons.
It has 20 electrons.
Why? The # of protons and electrons is the same. Ions aren't on the periodic table.
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