1)a 2)D 3)a. I think the answers are
Nitrogen and carbon dioxide
Cosmic, or background, radiation is the small amount of high energy radiation which is mostly left over from the big bang or from supernovas. It is mostly single protons, but also alpha particles and even sometimes heavier elements. It can also refer to the low levels of electromagnetic radiation present all over the universe.
The electrostatic force between two charges q1 and q2 is given by

where

is the Coulomb's constant

is the distance between the two charges.
In our problem, the two charges are two electrons, so their charges are equal and equal to

By substituting these values, we find the intensity of the force between the two electrons:

This is the magnitude of the force each electron exerts to the other one. The direction is given by the sign of the charges: since the two electrons have same charge, they repel each other, so the force exerted by electron 1 is toward electron 2 and viceversa.