Which of the following determines the strength of the force and gravity between two objects? choose all that apply
a) the speeds of the objects
b) the masses of the objects
c) the distance between the objects
d) the volume of the objects

i think it's c. i'm not sure but i think so.

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.