PLEASE ANSWER Which has the smallest atomic radius and why?

a
Sodium because the element's nucleus has the greatest positive charge of the four elements; so there is a stronger force of attraction that pulls the electrons closer to the nucleus.
b
Argon because the element's nucleus has the greatest positive charge of the four elements; so there is a stronger force of attraction that pulls the electrons closer to the nucleus.
c
Phosphorus because the element's nucleus has the greatest positive charge of the four elements; so there is a stronger force of attraction that releases the electrons closer to the nucleus.
d
Aluminum because the element's nucleus has the smallest positive charge of the four elements; so there is a stronger force of attraction that pulls the electrons closer to the nucleus