Which pair of atoms has the highest electron negativity

You forget to include the pair of atoms. But I found similar questions that asks about the following pairs:

H – S 
H – Cl 
N – H 
O – H 
C – H

To be able to answer, we must find out the electronegativity of each atom

Electronegativity of H = 2.2 
Electronegativity of S = 2.58
Electronegativity of N = 3.04
Electronegativity of Cl = 3.16 
Electronegativity of O = 3.5 
Electronegativity of C = 2.55 

Since all these atoms are paired with H, and they all have electronegativity greater than H, the atom with the highest electronegativity (O) would pair with H to have the greatest electronegativity difference.

The answer is therefore, O – H 

Ithink is d. physical property