• Gain and phase curves decrease continuously with frequency
• BGain curve increases and phase curve decreases with frequency
• CGain curve and phase curve both increase with frequency
• DGain curve decreases and phase curve increases with frequency

The (simplified) Bode stability criterion requires that both the open-loop gain (AR) and phase angle curves decrease monotonically (continuously) with increasing frequency, so that the gain and phase crossover frequencies are each crossed only once.