Alpha radiation consists of helium nuclei

Steps:

• Identify alpha radiation as one of three main types in radioactive decay: alpha, beta, gamma.
• Recall alpha particles are ejected from unstable nuclei during decay.
• Note alpha particles have a charge of +2 and mass of 4 atomic units, matching helium-4.
• Confirm alpha emission reduces atomic number by 2 and mass number by 4.

Why B is correct:

• By definition, alpha radiation consists of helium nuclei (two protons and two neutrons), as established in nuclear physics.

Why the others are wrong:

• A: Fast-moving protons are hydrogen nuclei, not the composite helium structure of alpha particles.
• C: Microwaves are electromagnetic waves, not ionizing particulate radiation like alpha.
• D: Radio waves are low-energy electromagnetic radiation, unrelated to nuclear decay particles.

Final answer: B