Final answer:
Chlorine (Cl) is the most electronegative of the elements listed, which include Li, Cs, and I, due to its position towards the upper right of the periodic table.
Step-by-step explanation:
Of the elements listed - Li (lithium), Cs (cesium), I (iodine), and Cl (chlorine) - chlorine (Cl) is the most electronegative. Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. The Pauling scale is a scale of electronegativities that places fluorine as the most electronegative element with cesium being one of the least. Electronegativity values increase from the bottom left to the top right of the periodic table. Hence, among the listed elements, Cl, which is a halogen located towards the upper right of the periodic table, has a higher electronegativity than I, Li, and Cs.