Based on their positions in the periodic table, which of the following elements would you expect to have the highest electronegativity value? astatine (at) barium (ba) chlorine (cl) magnesium (mg)

The correct answer is:  [C]:  "chlorine (Cl) " .

Note:  In the Periodic Table of Elements"

↑ electronegativity increases ;
→ electronegative increases ; 

and among the answer choices provided:
 
 →  "chlorine (Cl)" is in the most "upper-right hand position" in the Periodic Table of Elements ; and as such, the correct answer choice.