Answer:
The correct answer is helium 4.
Step-by-step explanation:
A positively charged particle, which comprises two protons and two neutrons is called an alpha particle. There is a similarity between the alpha particle and a helium atom as helium atom also possess mass number, that is, no of protons plus no of neutrons as 4, and atomic number, that is, number of protons a 2.
Therefore, it can be said that an alpha particle is also considered as a nucleus of helium isotope.