The correct option is B Argon
Elements combine inorder to attain the electronic configuration of the nearest noble gases.
The atomic number of chlorine is 17. It has 7 electrons in its valence shell. It requires one more electron to attain the stable electronic configuration of the nearest noble gas i.e., argon (atomic number =18).
So, on combining with other elements, chlorine acquires the electronic configuration of argon to attain stability.