5. Four of the following coordinate pairs are the corners of a square. Which is the odd one out?
A $(4,1)$
B $(2,4)$
C $(5,6)$
D $(3,5)$
$\mathrm{E}(7,3)$
5. D First note that $A B=\sqrt{13}, A C=\sqrt{26}, A D=\sqrt{17}$ and $A E=\sqrt{13}$. Thus $A B=A E$.
Note also that $B C=\sqrt{13}$ and $C E=\sqrt{13}$. Therefore $A B C E$ is a rhombus.
Finally, $B E=\sqrt{26}$, so $A B C E$ is a rhombus with two equal diagonals and hence is a square.
So $(3,5)$ is the odd point out.