The correct option is C Chlorine
The table given below shows the electronic configuration of given elements and the number of electrons present in their outermost shell. ElementsElectronic configurationElectrons in outermost shellSodium(2,8,1)1Oxygen(2,6)6Chlorine(2,8,7)7Neon(2,8)8
From the table, it is clear that chlorine (Cl) is the element among the given options whose atom needs only one electron to attain noble gas configuration.