Final answer:
Kelsey used the Protective extension backwards reflex as she fell, which is a natural response to protect oneself from potential harm during a fall. Reflex actions such as these are automatic and crucial for our safety in sudden situations. These types of reflexes are seen in human development with examples including the Moro reflex and grasping reflex in infants.
Step-by-step explanation:
The scenario described involves Kelsey using a reflex action as she falls backward. The correct answer to which reflex she utilized is: 3) Protective extension backwards. This reflex is part of our natural response to losing balance where we extend our arms to protect ourselves from injury upon falling. It's an automatic response that helps mitigate damage from a fall.
Reflexes like the Moro reflex or the grasping reflex are important in human development, particularly in infants. These reflexes facilitate infants in maintaining close physical contact with their caregivers and also in their basic need for constant physical contact. The Moro reflex, in particular, consists of an infant suddenly spreading out the arms, pulling them back in, and usually crying in response to a sense of falling.
When it comes to reflex actions and impulse, such as the situation where you would bend your knees while jumping off a bench, the correct response, according to the impulse-momentum theorem, would be a. Bending your knees increases the time over which the impact occurs, thereby reducing the force of the impact. This explains why it's a natural and protective response to bend one's knees when anticipating an impact.