He atoms in a sample of carbon must contain nuclei with the same number of a) electrons. b) neutrons. c) nucleolus. d) protons.

Protons

Explanation:

Atoms are the smallest particles of elements that can take part in chemical reactions.They are made of sub-atomic particles: protons, neutrons, and electrons.Neutrons and protons are found in the nucleus of the atom while electrons are found orbiting around the nucleus in the energy levels of the atom.Elements may contain several isotopes, these are atoms of the same element that have the same atomic number but a different mass number. In other words, isotopes have an equal number of protons but a different number of neutrons. Therefore, all atoms of a sample carbon must have a similar atomic number or an equal number of protons in their nuclei