All atoms of the same element have :

A

different numbers of electrons.

B

the same number of protons.

C

different numbers of neutrons.

D

different numbers of protons.

E

the same number of neutrons.

Atoms of the same element have the same atomic number so the number of protons (and electrons) are same. But they have same or different mass number (like that for isotopes) . Different mass number will have different number of neutrons.