I think it is c density and temperature
Answer:

Explanation:
The electric force on a charged particle is given by

where
q is the charge of the particle
E is the strength of the electric field
In this problem, we have
is the electric field strength
is the charge of the calcium ion
Therefore, the electric force exerted on the calcium ion is

Answer:C, Atoms of iron are different from atoms of nickel.
Explanation:All the atoms that make up each type of element are alike, and they are different from the atoms that make up every other type of element. So the element iron is different from the element nickel because the atoms that make up the iron are different from the atoms that make up the nickel.