What is the primary feature of an FX side leap?

The primary feature of an FX side leap is indeed the floating side movement through the air. In this particular skill, the gymnast performs a jump that emphasizes a lateral motion, creating the appearance of floating during the execution. The grace and technique involved in a side leap require the gymnast to maintain body alignment and control throughout the movement, allowing them to achieve that expansive, airy quality in their leap. This aspect is crucial in conveying the aesthetic appeal and technical proficiency expected in gymnastics routines, particularly in floor exercise, where choreography and artistic expression play significant roles.

While the other options also describe aspects of gymnastics movements, they do not capture the essence of what defines the side leap specifically. The jump might involve both feet at takeoff, but the hallmark is the lateral float through the air, making the correct answer the one that highlights this unique characteristic.