Answer:
a. proton
Step-by-step explanation:
Proton -
It is on of the subatomic particle of the atom , it is positively charged , with the symbol of p⁺ , i.e. , a single positive charge .
The mass of proton and the neutrons together contributes to the mass of the atom .
All the elements have their specific number of proton and mass number , denoted by Z .
Hence , from the given options the correct answer is a. proton .