Option A: Unique solution
The equations $2x + 1 = 0$ gives $x = -\frac{1}{2}$ and $3y - 5 = 0$ gives $y = \frac{5}{3}$. These are independent equations, each with exactly one value, so the system has a unique solution.
Although each equation has only one variable, together they form a consistent pair with a single ordered pair solution $\left(-\frac{1}{2},\ \frac{5}{3}\right)$. Examiners expect students to recognise that one equation in $x$ and one in $y$ (with no contradiction) always yields exactly one solution. Do not confuse "one variable each" with "no solution" or "infinite solutions."