Step-by-step explanation
An alpha particle is one that has two protons and two neutrons tightly bound together.
Now, the atomic number corresponds to the number of protons that the particle has, therefore, having two protons, the atomic number will be equal to 2.
The atomic mass corresponds to the mass of the nucleus, ie the sum of protons and neutrons. Therefore, the atomic mass will be 2+2=4.
Answer: B. A particle with an atomic number of 2 and an atomic mass of 4.