Which of the following is a crucial characteristic of aircrew anti-G suits?

Pressure application to the lower body is indeed a crucial characteristic of aircrew anti-G suits. These suits are specifically designed to help combat the effects of gravitational forces experienced during high-speed maneuvers and rapid acceleration. By applying pressure to the lower body, the suit prevents blood from pooling in the legs and abdomen, which helps maintain blood flow to the brain and reduces the risk of G-induced Loss Of Consciousness (GLOC). This capability is essential for pilots and aircrew operating in high-performance aircraft where extreme G-forces are encountered.

While high flexibility, lightweight fibers, and water-resistance are beneficial features that may enhance comfort and performance, the primary function of the anti-G suit is its ability to apply pressure effectively to critical areas of the body during G-force exposure.