What is the most polar covalent bond? Which polar covalent bond of the following:

Cl-F

S-O

P-N

C-Cl

It's trivia - I guess. And I got it wrong. 

Electronegativity list was given for the following:
F, O, Cl, N, S, C, H, P

My wrong reasoning was:
why would two highly electronegative atoms bond with each other. Even they did, given their high electronegativity as both pull the electron cloud to each side (tug of war, weak dipole moments) with much strength by forming a weak bond. I refused to consider the difference between electronegativity of the species. (Even I did, S-O would be the highest). 

I applied the same to S-O and P-N as well.
C-Cl was the pick and bad!

C-Cl has a acceptable dipole moment given C's less en 2.55 and Cl's high en. 3.16. The size of atoms wise, Cl-F is shorter compared to C-Cl. Which is questionable.

I checked few other related questions and answers, such as this peculiar one and this.

As I read ron's answer (the latter), the concept is not about a compound like CCl4 which negates the polarity between C-Cl bonds in the tetrahedral geometry. Thus C-Cl is a polar covalent bond. (isn't it?)

Where did I go wrong in reasoning, what did I miss?
PS: Not homework but some theory revision questions. Trying to reinstate/expand the understanding of concepts.
There are various electronegativity scales. 

Electronegativity vales from Wikipedia

$$\newcommand{\d}[2]{#1.&amp;\hspace{-1em}#2}
\begin{array}{lrl}
\hline
\text{Element} &amp; \text{Pauling} &amp; \text{Allen}&amp; \\
\hline
\text{H}  &amp; 2.20  &amp; 2.30 \\
\text{C}  &amp; 2.55  &amp; 2.544 \\
\text{N}  &amp; 3.04  &amp; 3.066 \\
\text{O}  &amp; 3.44  &amp; 3.610 \\
\text{F}  &amp; 3.98  &amp; 4.193 \\
\text{P}  &amp; 2.19 &amp; 2.253 \\
\text{S}  &amp; 2.58 &amp; 2.589\\
\text{Cl} &amp; 3.16 &amp; 2.896 \\
\hline
\end{array}
$$

The compounds are all binaries, so the polarity, $\mu$, is equal to the difference in charge, $\delta$, times the distance, $d$, between ions ($\mu = \delta \cdot d$). Only given a table of electronegativities, the first level of analysis would be to assume that all the bond lengths were equal and that that the polarity would simply be a function of the difference in electronegativity. The differences are thus:

$$\newcommand{\d}[2]{#1.&amp;\hspace{-1em}#2}
\begin{array}{lrl}
\hline
\text{Element} &amp; \text{Pauling} &amp; \text{Allen}&amp; \\
\hline
\Delta\text{Cl-F}  &amp; 0.82  &amp; 1.297 \\
\Delta\text{S-O}  &amp; 0.86  &amp; 1.021 \\
\Delta\text{P-N}  &amp; 0.85  &amp; 0.813 \\
\Delta\text{C-Cl}  &amp; 0.61  &amp; 0.352 \\
\hline
\end{array}
$$

So on the Pauling scale S-O should be the most polar, but on the Allen scale Cl-F should be the most polar.