Chapter 5.3, Problem 2ED

In Example 2B we saw that there was no optimal solution for the problem of maximizing the objective function $z$ over the feasible region $S$. We want to add an additional constraint to modify the feasible region so that an optimal solution for the maximization problem does exist. Which of the following constraints will accomplish this objective?

$\left(\text{A}\right)x\le 20\left(\text{B}\right)y\ge 4\left(\text{C}\right)x\le y\left(\text{D}\right)y\le x$