The correct answer is: A. Protons
Protons are positively charged particles that are found in the nucleus of an atom. The number of protons in an atom is called the atomic number. The atomic number determines the chemical element of an atom. For example, all atoms with 6 protons in their nucleus are carbon atoms.
Electrons are negatively charged particles that are found outside the nucleus of an atom. The number of electrons in an atom is equal to the number of protons in the nucleus. This is because atoms are electrically neutral, so the positive charge of the protons must be balanced by the negative charge of the electrons.
Neutrons are neutral particles that are also found in the nucleus of an atom. The number of neutrons in an atom can vary, and this variation is what gives rise to different isotopes of the same element. For example, carbon has two naturally occurring isotopes: carbon-12, which has 6 neutrons, and carbon-13, which has 7 neutrons.
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