Concept:An alpha particle is a helium nucleus represented by the Greek letter α.Explanation:An alpha particle contains 2 protons and 2 neutrons.It is therefore the same as a helium-4 nucleus, written as 24He2+ or simply α.The symbol β stands for a beta particle.The symbol γ stands for gamma radiation.The symbol δ is used for delta particles or delta rays.Hence, the alpha particle is shown by option A.Answer:A. α