Compound with maximum ionic character is formed from:
A. Na and Cl
B. Cs and F
C. Cs and I
D. Na and F

Hint: Ionic character depends on the electronegativity difference between cation and anion of the compounds. Moreover it depends on the size too, cations need to be large and anions as small as possible.

Complete step by step answer:
-Ionic character is set in terms of "greater ionic character" and "lower ionic character". If a molecule has an increasing or the next difference in electronegativities, then there's a greater ionic character. If the difference in electronegativity is decreasing (becoming more similar), which means there's lower ionic character, and greater covalent character.Ionic character is set in terms of "greater ionic character" and "lower ionic character". If a molecule has an increasing or the next difference in electronegativities, then there's a greater ionic character. If the difference in electronegativity is decreasing (becoming more similar), which means there's lower ionic character, and greater covalent character.
-Electronegativity measures the tendency of an atom to draw in a shared pair of electrons. An atom's electronegativity is littered with both its number and therefore the distance at which its valence electrons reside from the charged nucleus. Electronegativity increases as you progress across the table from left to right. This happens thanks to a greater charge on the nucleus, causing the electron bonding pairs to be very drawn to atoms placed further right the table. Electronegativity decreases as you progress down the table.
-Ionic character depends upon, electronegativity difference between cation and anion of compound. As these differences increase, ionic character increases. Larger the scale of cation and smaller the dimensions of anion, more is that the electronegativity difference and more is that the ionic character.

So CsF is the most ionic among all.

Note: In the periodic table, Fluorine (F) is the most electronegative element and it is also a small size anion. Therefore it forms the most ionic product, as according to Fajans rule a large cation and small anion are required for ionic character.