Answer:
B protons
Step-by-step explanation:
- The atomic number of a nucleus (often labelled with Z) is the number of protons inside the nucleus
- The mass number of a nucleus (often labelled with A) is the sum of the protons and the neutrons inside the nucleus
- The number of electrons in a neutral atom is equal to the number of protons inside the nucleus
Therefore, the correct answer is
B protons
However, A (electrons) could also be considered correct if we are talking about a neutral atom.