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A discrete-time all-pass system has two of its poles at $0.25\angle 0^{\circ}$ and $2\angle 30^{\circ}$. Which one of the following statements about the system is TRUE?

1. It has two more poles at $0.5\angle 30^{\circ}$ and $4\angle 0^{\circ}.$
2. It is stable only when the impulse response is two-sided.
3. It has constant phase response over all frequencies.
4. It has constant phase response over the entire $\text{z-plane}$.

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