Step 1: Concept
In Simple Harmonic Motion, the magnitude of acceleration is related to displacement by $a = \omega^2 x$.
Step 2: Meaning
Angular frequency ($\omega$) can be found by taking the square root of the ratio of acceleration to displacement.
Step 3: Analysis
$\omega^2 = a/x = 48.0 / 3.0 = 16$.
$\omega = \sqrt{16} = 4~s^{-1}$.
Step 4: Conclusion
Hence, the angular frequency is 4.
Final Answer: (E)