The strongest electropositive element among the following is:

Electropositivity refers to the tendency of an atom to lose electrons and form positive ions.
In the periodic table:

* Electropositivity increases down a group because the atomic radius increases and the nuclear attraction on valence electrons decreases.
* Electropositivity decreases across a period from left to right because the nuclear charge increases.

Among the given options, Lithium ($\text{Li}$), Potassium ($\text{K}$), and Cesium ($\text{Cs}$) belong to Group 1 (alkali metals), which are inherently more electropositive than Group 2 elements like Magnesium ($\text{Mg}$). Within Group 1, Cesium ($\text{Cs}$) lies furthest down the group, meaning it has the largest atomic size and lowest ionization energy, making it the strongest electropositive element.