The correct statement is option 4: Both protons and neutrons can reside inside the nucleus of an atom. The nucleus of an atom is a small, dense core located at the center of the atom. It contains two types of subatomic particles known as protons and neutrons. Protons have a positive charge, while neutrons have no charge. Electrons, on the other hand, are negatively charged particles that orbit around the nucleus in regions called electron shells or energy levels.

Option 1 is incorrect because electrons do not reside inside the nucleus; they exist outside the nucleus in the electron shells.

Option 2 is incorrect because although electrons do reside outside the nucleus, protons are the only particles found inside the nucleus.

Option 3 is incorrect because neutrons, as mentioned earlier, also reside inside the nucleus along with protons.

Alert - correct answer should be: Option 4.