An ideal LC circuit oscillates freely. If $L = 4\,\text{mH}$ and $C = 25\,\mu\text{F}$, the angular frequency of oscillation is:

For a free LC oscillation $\omega = 1/\sqrt{LC}$. We have $LC = 4 \times 10^{-3} \times 25 \times 10^{-6}$. So $LC = 10^{-7}\,\text{s}^2$. so $\sqrt{LC} = 10^{-3.5}\,\text{s}$ and $\omega = 10^{3.5} \approx 3162\,\text{rad/s}$. Rounded to the nearest power of ten this is $10^3\,\text{rad/s}$.