Answer:
d. proton
Step-by-step explanation:
The atomic number is usually regarded as the proton number. The atomic number is equal to the number of protons that is found in the nucleus of every atom in an element. Let say we have an element Z with an atomic number. Changing the number of protons would definitely change the element Z and it properties.
Therefore, the subatomic particle that plays the greatest role in determining the properties of an element is Proton.