Final answer:
The number of protons in an atom determines the element it belongs to, while the presence of electrons allows atoms to do chemistry.
Step-by-step explanation:
The number of protons in an atom's nucleus determines what element it belongs to. This is because the atomic number of an element is equal to the number of protons in its atoms. For example, any atom with six protons is the element carbon with an atomic number of 6.
The presence of electrons allows atoms to do chemistry. Electrons are negatively charged particles that orbit the nucleus of an atom. The interactions between the electrons of different atoms govern chemical reactions.
So, option D) electrons, protons, is the correct answer.