The correct answer is that sulfur has a smaller radius and one proton more than phosphorus.
This is because if sulfur is to the immediate right of phosphorus, it must have one more proton due to the fact that the periodic table is arranged by increasing atomic number (number of protons) of its elements.
The atomic radius of elements decreases across a period because the greater number of protons has an increased “pull” on the electrons, pulling them in closer to the nucleus and thus making the atomic radius smaller.
Hope this helps!