Final answer:
The rotational inertia of a bent leg is less due to reduced mass distribution from the axis of rotation, adhering to the principle of conservation of angular momentum, which relates moment of inertia and angular velocity.Therefore the correct option is B) Reduced mass distribution.
Step-by-step explanation:
When swinging your leg from your hip, the rotational inertia of the leg is less when it is bent because of Reduced mass distribution. The moment of inertia depends on the distance of the mass from the axis of rotation. By bending the leg, the mass of the leg is closer to the hip joint, which decreases the leg's moment of inertia.
This concept is similar to a figure skater spinning faster with arms and legs pulled in, due to conservation of angular momentum. Reducing the moment of inertia while maintaining angular momentum results in a greater angular velocity.
For instance, while exercising in a fitness center, if you lift a weight with a bent leg, the moment of inertia is smaller, and a smaller torque is needed to achieve a particular angular acceleration.
Similarly, when a figure skater or dancer brings their limbs closer to the axis of their body, they spin faster because their reduced moment of inertia leads to an increase in angular velocity (provided that angular momentum is conserved).