Question

Be, C, O, B, Al which is the most electropositive element among these

Answer 1

Here you're asking about the electropositive element :-

Electropositive element :- The electropositive elements are those which is to be considered as a very low electronegativity .

First we have to arrange them in increasing atomic numbers :-

 → Be , B, C, O , Al 

Here Beryllium is the Most Electropositive element .


Reason/ Explanation :-

Among these elements , Be . B , C , O , Lie in the same period , and we know as we move across the period ,The electronegativity decreases and the electropositivity increases, due to decrease in Nuclear charge.
Thus Beryllium (Be) is the Most electropositive element among them. 

Aluminium lies below the Boron (B) in periodic table thus it has more electropositivity then Boron, but less then Be. 
[Note :- But as far as you must know Alkali Metals are most electropositive Elements ].

Hence the most electropositive element among them is (Beryllium) Be.



Hope it Helps.

Answer 2

Answer: Be is the most electropositive element .

Explanation: It is because electropositive element is one with very low electronegativity.