1. What first initiated the formation of galaxies? areas of greater gas density
expansion forces on the gas
concentration of dark matter
2.
In what direction is the universe moving?
condensing toward the center
expanding out from the center
at equilibrium with the center
3.Which factor suggests that an elliptical galaxy will form?
formed in isolation
higher angular momentum
faster cooling rate

a:

by the combination of an unlimited number of elements

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.