What is so special about the combination e/m ? Why do we not simply talk of e and m separately ?

Question

$\begin{array}{1 1} \text{e and m always occur together in all equations , related to motion of the electron } \\ \text{e and m always occur separately in all equations , related to motion of the electron } \\ \text{The value of e/m is easier to find out} \\ \text{ None of the above } \end{array}$