Answer
The function is odd.
Work Step by Step
We have that $E(-x)=E(x)$ and $O(-x)=-O(x)$.
Let $\Phi=E/O$. Then
$$\Phi(-x)=\frac{E(-x)}{O(-x)}=\frac{E(x)}{-O(x)}=-\frac{E(x)}{O(x)}=-\Phi(x)$$
which means that the function is odd.
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