Answer: Option (b) is the correct answer.
When there will be completely filled orbital of an atom then it neither needs to lose or gain an electron in order to attain stability. This is because it is already stable due to completely filled orbital.
Therefore, it means that the element will be inert in nature.
For example, helium is a noble gas and its electronic configuration is .
As it has completely filled s-orbital so, it is stable in nature.
Whereas when an element does not have completely filled orbital then it needs to gain stability by gaining or losing an electron. This is what determines the reactivity of an element.
Thus, we can conclude that an element which will not combine chemically is inert.