In biventricular heart failure, which statement is true?

A. The ventricles work simultaneously, not alternately, and both failing leads to compromised cardiac output. B. Biventricular heart failure involves both the left and right ventricles, not just the left. C. An ejection fraction above 50% is considered normal; in heart failure, especially biventricular, it is often reduced. D. Biventricular heart failure means both ventricles are impaired, often resulting in a significantly reduced ejection fraction and poor cardiac function.