A student measures the volume of a rock, and then repeats the measurement two times. For the three measurements to be very precise, what must be true about them? A. The measurements must be very close to the true volume of the rock.

B. The measurements must be very close to one another.

C. At least one of the measurements must be equal to the true volume of the rock.

D. The three measurements must be reported in whole numbers, not decimals.

i think b

Explanation:

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.