Accurate answer is (b) Unstable system
Discover the easiest explanation: The given circuit is used in inverting mode and produce a phase shift of 180^o. For two corner frequency, the maximum phase shift associated with gain AoL is -180^o which makes total phase shift = 0 and for some value of ß, the magnitude of Aß becomes unity. In this case the amplifier begins to oscillate as both magnitude and phase conditions are satisfied. Thus, the circuit enter into verge of instability.