Aircrews are required to don G-suits when anticipating how many Gs during any portion of a sortie?

Aircrews are required to don G-suits when anticipating 2 Gs during any portion of a sortie because this level of gravitational force can start to affect blood circulation and the body's ability to function properly. At this threshold, wearing a G-suit helps prevent the onset of G-induced loss of consciousness (GLOC) by assisting in maintaining blood flow to the brain during rapid acceleration or high-speed maneuvers, which are common in military aviation. This precaution is essential for maintaining pilot performance and ensuring safety during flight operations, as the physical effects of higher G forces can become increasingly severe.

While the other choices involve lower or higher Gs, they do not align with the established safety protocols for G-suit usage, making 2 Gs the critical point where G-suits become necessary for crew protection.