The correct option is (y- x) e.

To understand why this is correct, we can look at the fundamental electrical charges of protons and electrons:

1. An electron carries a negative elementary charge, which is represented as:
$-e$

2. A proton carries a positive elementary charge, which is represented as:
$+e$

If an object contains
$x$
electrons, the total negative charge contributed by these electrons is:
$-xe$

Similarly, if the object contains
$y$
protons, the total positive charge contributed by these protons is:
$+ye$

The net charge on the object is the algebraic sum of the total positive charges and the total negative charges:

$\text{Net Charge}=\left(\text{Total Charge of Protons}\right)+\left(\text{Total Charge of Electrons}\right)$

Substituting the expressions, we get:

$\text{Net Charge}=ye+(-xe)$

By factoring out the common elementary charge term
$e$
we obtain the final simplified expression:

$\text{Net Charge}=(y-x)e$

This matches the correct option.