Answer
(b) $H_2O$ has the most polar bonds.
Work Step by Step
We can use Figure 8.9 to calculate the difference between the electronegativity of each pair of atoms.
(a) 2.4 - 2.1 = 0.3
(b) 3.5 - 2.1 = 1.4
(c) 3.5 - 2.5 = 1.0
(d) 3.0 - 2.0 = 1.0
(e) 3.0 - 2.1 = 0.9
The one with greater difference of electronegativity is (b) $H_2O$. Therefore it has the most polar bonds.
