To find out the electronegativity of each pair, work it out by listing them.
H = 2.2
S = 2.1
N = 3.0
Cl = 3.0
O = 3.5
C = 2.5
H – S -> 2.2 - 2.1 = 0.1
H – Cl -> 2.2 - 3.0 = -0.8
N – H -> 3.0 - 2.2 = 0.8
O – H -> 3.5 - 2.2 = 1.3
C – H-> 2.5 - 2.2 = 0.3
So, the pairs that has the highest electronegativity is H-Cl and N-H.
