CAT 2025 Number System — Previous Year Question

Let $3 \leq x \leq 6$ and $\lfloor x^2 \rfloor = \lfloor x \rfloor^2$, where $\lfloor x \rfloor$ is the greatest integer not exceeding $x$. If set $S$ represents all feasible values of $x$, then a possible subset of $S$ is: