Alpha Particle Composition Steps:

• Recall that an alpha particle is emitted during radioactive decay and is identical to a helium-4 nucleus.
• Identify the structure of a helium-4 nucleus: it has an atomic number of 2 (protons) and mass number of 4 (protons + neutrons).
• Calculate neutrons: mass number minus protons = 4 - 2 = 2 neutrons.
• Confirm no electrons are present, as it is a bare nucleus.

Why A is correct:

• An alpha particle is defined as the nucleus of a helium-4 atom, consisting of exactly two protons and two neutrons.

Why the others are wrong:

• B: Electrons are not part of an alpha particle; it has no electrons, and four neutrons would mismatch the mass.
• C: Alpha particles have two, not four, neutrons.
• D: Includes electrons, which are absent in the nucleus; also only two neutrons total.

Final answer: A